wikilangs/bg

Bulgarian - Wikilangs Models

Comprehensive Research Report & Full Ablation Study

This repository contains NLP models trained and evaluated by Wikilangs, specifically on Bulgarian Wikipedia data. We analyze tokenizers, n-gram models, Markov chains, vocabulary statistics, and word embeddings.

📋 Repository Contents

Models & Assets

• Tokenizers (8k, 16k, 32k, 64k)
• N-gram models (2, 3, 4, 5-gram)
• Markov chains (context of 1, 2, 3, 4 and 5)
• Subword N-gram and Markov chains
• Embeddings in various sizes and dimensions (aligned and unaligned)
• Language Vocabulary
• Language Statistics

Analysis and Evaluation

• 1. Tokenizer Evaluation
• 2. N-gram Model Evaluation
• 3. Markov Chain Evaluation
• 4. Vocabulary Analysis
• 5. Word Embeddings Evaluation
• 6. Morphological Analysis (Experimental)
• 7. Summary & Recommendations
• Metrics Glossary
• Visualizations Index

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1. Tokenizer Evaluation

Results

Vocab Size	Compression	Avg Token Len	UNK Rate	Total Tokens
8k	3.452x	3.45	0.0493%	2,552,470
16k	3.809x	3.81	0.0544%	2,313,214
32k	4.120x	4.12	0.0589%	2,138,945
64k	4.373x 🏆	4.37	0.0625%	2,015,292

Tokenization Examples

Below are sample sentences tokenized with each vocabulary size:

Sample 1: Часово отместване UTC-11 се използва в: : Американска Самоа, Атол Мидуей : Ниуе ...

Vocab	Tokens	Count
8k	▁ча сово ▁от мест ване ▁utc - 1 1 ▁се ... (+17 more)	27
16k	▁ча сово ▁от мест ване ▁utc - 1 1 ▁се ... (+15 more)	25
32k	▁ча сово ▁от местване ▁utc - 1 1 ▁се ▁използва ... (+13 more)	23
64k	▁часово ▁отместване ▁utc - 1 1 ▁се ▁използва ▁в : ... (+9 more)	19

Sample 2: Synodontis ouemeensis е вид лъчеперка от семейство Mochokidae. Разпространение В...

Vocab	Tokens	Count
8k	▁s yn od ont is ▁o u em e ensis ... (+22 more)	32
16k	▁syn odont is ▁o u em e ensis ▁е ▁вид ... (+20 more)	30
32k	▁syn odont is ▁ou em e ensis ▁е ▁вид ▁лъчеперка ... (+19 more)	29
64k	▁synodontis ▁ou eme ensis ▁е ▁вид ▁лъчеперка ▁от ▁семейство ▁mochokidae ... (+13 more)	23

Sample 3: Orthotomus derbianus е вид птица от семейство Cisticolidae. Разпространение Видъ...

Vocab	Tokens	Count
8k	▁or th ot om us ▁der b ian us ▁е ... (+22 more)	32
16k	▁or th ot omus ▁der b ianus ▁е ▁вид ▁птица ... (+17 more)	27
32k	▁orth ot omus ▁der b ianus ▁е ▁вид ▁птица ▁от ... (+14 more)	24
64k	▁orth ot omus ▁der b ianus ▁е ▁вид ▁птица ▁от ... (+13 more)	23

Key Findings

• Best Compression: 64k achieves 4.373x compression
• Lowest UNK Rate: 8k with 0.0493% unknown tokens
• Trade-off: Larger vocabularies improve compression but increase model size
• Recommendation: 32k vocabulary provides optimal balance for production use

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2. N-gram Model Evaluation

Results

N-gram	Variant	Perplexity	Entropy	Unique N-grams	Top-100 Coverage	Top-1000 Coverage
2-gram	Word	246,747	17.91	2,004,902	5.8%	16.2%
2-gram	Subword	385 🏆	8.59	20,810	61.1%	97.4%
3-gram	Word	1,033,483	19.98	4,251,847	2.5%	8.2%
3-gram	Subword	3,528	11.78	189,319	23.2%	62.6%
4-gram	Word	2,692,464	21.36	7,308,829	1.5%	5.1%
4-gram	Subword	21,676	14.40	1,191,303	10.4%	32.6%
5-gram	Word	2,278,792	21.12	5,264,454	1.8%	5.4%
5-gram	Subword	93,842	16.52	4,256,227	5.4%	19.0%

Top 5 N-grams by Size

2-grams (Word):

Rank	N-gram	Count
1	през г	371,674
2	да се	178,835
3	през година	109,499
4	външни препратки	108,119
5	е на	90,144

3-grams (Word):

Rank	N-gram	Count
1	по време на	72,585
2	източници външни препратки	52,888
3	пр н е	38,682
4	може да се	32,598
5	през г е	28,945

4-grams (Word):

Rank	N-gram	Count
1	разпространение видът е разпространен	11,928
2	видът е разпространен в	11,811
3	може да се отнася	9,394
4	външни препратки официален сайт	9,248
5	застрашен от изчезване разпространение	9,061

5-grams (Word):

Rank	N-gram	Count
1	разпространение видът е разпространен в	11,030
2	може да се отнася за	8,323
3	е вид птица от семейство	8,165
4	източници външни препратки уебсайт на	7,757
5	външни препратки уебсайт на общината	7,230

2-grams (Subword):

Rank	N-gram	Count
1	а _	22,221,689
2	н а	13,044,169
3	и _	12,174,707
4	_ с	10,248,868
5	_ н	9,602,446

3-grams (Subword):

Rank	N-gram	Count
1	н а _	8,421,175
2	_ н а	7,714,836
3	_ п р	3,824,613
4	т а _	3,691,871
5	т о _	3,556,816

4-grams (Subword):

Rank	N-gram	Count
1	_ н а _	5,969,377
2	а т а _	2,454,178
3	_ о т _	2,129,103
4	а _ н а	1,914,071
5	_ п р е	1,889,917

5-grams (Subword):

Rank	N-gram	Count
1	а _ н а _	1,515,525
2	е _ н а _	949,109
3	_ п р е з	882,206
4	п р е з _	849,611
5	о _ н а _	755,344

Key Findings

• Best Perplexity: 2-gram (subword) with 385
• Entropy Trend: Decreases with larger n-grams (more predictable)
• Coverage: Top-1000 patterns cover ~19% of corpus
• Recommendation: 4-gram or 5-gram for best predictive performance

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3. Markov Chain Evaluation

Results

Context	Variant	Avg Entropy	Perplexity	Branching Factor	Unique Contexts	Predictability
1	Word	0.9743	1.965	12.25	1,896,771	2.6%
1	Subword	1.0920	2.132	7.98	9,126	0.0%
2	Word	0.3814	1.303	2.47	23,216,480	61.9%
2	Subword	0.7778	1.714	5.53	72,830	22.2%
3	Word	0.1657	1.122	1.39	57,272,367	83.4%
3	Subword	0.8207	1.766	4.91	403,072	17.9%
4	Word	0.0723 🏆	1.051	1.13	79,394,777	92.8%
4	Subword	0.7498	1.682	3.81	1,979,446	25.0%

Generated Text Samples (Word-based)

Below are text samples generated from each word-based Markov chain model:

Context Size 1:

1. на излезли преди тази система от общинския център е най доброто от контекстовото запитване за написв...
2. в миналото корабите от своето поведение и актриси актьори рок група в колекциониране на военноморска...
3. и денчевци и е посрещала годеницата на черноморец бургас община палеор φούφας антиполохагос атина за...

Context Size 2:

1. през г тъй като години българия медал за на барила през г в битката е част от
2. да се шуми около връзката ѝ с република българия собствеността на международна научна конференция га...
3. външни препратки официален сайт схема на телескопа е било напълно елиминирано съмнението на ръководс...

Context Size 3:

1. по време на празничния сезон и стачката в метрото в токио vx не се използва от национално музикално
2. източници външни препратки официален сайт на метеор първите ѝ постановки са дипломният ѝ спектакъл с...
3. пр н е и са изключително популярни на балканите и втората най обща сред мъжете по онова време

Context Size 4:

1. разпространение видът е разпространен в малави мозамбик и j placidochromis johnstoni in iucn iucn re...
2. видът е разпространен в демократична република t lamprologus lethops in iucn iucn red list of threat...
3. може да се отнася до фердинандо i де медичи за да приюти извънбрачните дъщери на алесандро за разлик...

Generated Text Samples (Subword-based)

Below are text samples generated from each subword-based Markov chain model:

Context Size 1:

1. _трхтвътва_бъно_
2. а_ma_верг._п_ц_м
3. ита_менизандиясн

Context Size 2:

1. а_преват_и_с_ко_к
2. на_сед_хеърши_ак:
3. и_от_стори_те_съе

Context Size 3:

1. на_кампийский_став
2. _на_от_вите_ръчепе
3. _прически_баваща_с

Context Size 4:

1. _на_шаламброзиеолог
2. ата_е_важна_космиче
3. _от_попов_конвойна_

Key Findings

• Best Predictability: Context-4 (word) with 92.8% predictability
• Branching Factor: Decreases with context size (more deterministic)
• Memory Trade-off: Larger contexts require more storage (1,979,446 contexts)
• Recommendation: Context-3 or Context-4 for text generation

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4. Vocabulary Analysis

Statistics

Metric	Value
Vocabulary Size	888,624
Total Tokens	105,654,230
Mean Frequency	118.90
Median Frequency	4
Frequency Std Dev	9303.24

Most Common Words

Rank	Word	Frequency
1	на	5,995,585
2	в	3,186,690
3	и	3,167,004
4	е	2,175,525
5	от	2,154,986
6	за	1,348,073
7	се	1,261,391
8	г	1,205,312
9	с	1,088,412
10	през	849,597

Least Common Words (from vocabulary)

Rank	Word	Frequency
1	кепевци	2
2	сарджовци	2
3	мъндън	2
4	талиевия	2
5	carbonato	2
6	tallio	2
7	разр	2
8	барутхана	2
9	азадлу	2
10	шталаг	2

Zipf's Law Analysis

Metric	Value
Zipf Coefficient	0.9425
R² (Goodness of Fit)	0.997405
Adherence Quality	excellent

Coverage Analysis

Top N Words	Coverage
Top 100	35.2%
Top 1,000	53.9%
Top 5,000	70.2%
Top 10,000	77.2%

Key Findings

• Zipf Compliance: R²=0.9974 indicates excellent adherence to Zipf's law
• High Frequency Dominance: Top 100 words cover 35.2% of corpus
• Long Tail: 878,624 words needed for remaining 22.8% coverage

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5. Word Embeddings Evaluation

5.1 Cross-Lingual Alignment

5.2 Model Comparison

Model	Dimension	Isotropy	Semantic Density	Alignment R@1	Alignment R@10
mono_32d	32	0.7975 🏆	0.3595	N/A	N/A
mono_64d	64	0.7851	0.2896	N/A	N/A
mono_128d	128	0.7344	0.2334	N/A	N/A
aligned_32d	32	0.7975	0.3609	0.1560	0.5140
aligned_64d	64	0.7851	0.2794	0.3420	0.7340
aligned_128d	128	0.7344	0.2326	0.4740	0.8180

Key Findings

• Best Isotropy: mono_32d with 0.7975 (more uniform distribution)
• Semantic Density: Average pairwise similarity of 0.2926. Lower values indicate better semantic separation.
• Alignment Quality: Aligned models achieve up to 47.4% R@1 in cross-lingual retrieval.
• Recommendation: 128d aligned for best cross-lingual performance

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6. Morphological Analysis (Experimental)

This section presents an automated morphological analysis derived from the statistical divergence between word-level and subword-level models. By analyzing where subword predictability spikes and where word-level coverage fails, we can infer linguistic structures without supervised data.

6.1 Productivity & Complexity

Metric	Value	Interpretation	Recommendation
Productivity Index	5.000	High morphological productivity	Reliable analysis
Idiomaticity Gap	-0.715	Low formulaic content	-

6.2 Affix Inventory (Productive Units)

These are the most productive prefixes and suffixes identified by sampling the vocabulary for global substitutability patterns. A unit is considered an affix if stripping it leaves a valid stem that appears in other contexts.

Productive Prefixes

Prefix	Examples
-пр	предхождащ, прихлупена, правнообвързващи

Productive Suffixes

Suffix	Examples
-а	исаака, жижавица, гамета
-та	гамета, лопатовидната, малинката
-те	врапчиште, древноиндийските, регресионните
-ите	древноиндийските, регресионните, циментовите
-ата	лопатовидната, малинката, покойницата
-ни	пълнозначни, шекони, капсулни
-ки	весегонски, гаговски, бачовски
-ия	шумния, напрежения, валутния

6.3 Bound Stems (Lexical Roots)

Bound stems are high-frequency subword units that are semantically cohesive but rarely appear as standalone words. These often correspond to the 'core' of a word that requires inflection or derivation to be valid.

Stem	Cohesion	Substitutability	Examples
лгар	2.07x	163 contexts	елгар, илгар, юлгар
нска	1.82x	254 contexts	анска, энска, юнска
анск	1.39x	921 contexts	данск, анска, банск
ийск	1.57x	389 contexts	бийск, ийски, лийски
нски	1.49x	508 contexts	янски, ански, онски
ълга	2.34x	39 contexts	дълга, бълга, ългаз
емвр	2.64x	21 contexts	ноемвр, декемвр, нпември
рски	1.42x	269 contexts	юрски, врски, ерски
точн	1.58x	134 contexts	точни, точно, точна
ичес	1.43x	204 contexts	бичес, уичес, ическ
остр	1.37x	215 contexts	остри, остро, остра
ение	1.49x	123 contexts	пение, шение, мение

6.4 Affix Compatibility (Co-occurrence)

This table shows which prefixes and suffixes most frequently co-occur on the same stems, revealing the 'stacking' rules of the language's morphology.

Prefix	Suffix	Frequency	Examples
-пр	-а	59 words	пріложіха, приложната
-пр	-те	21 words	притеснявайте, профилиращите
-пр	-та	20 words	приложната, притежаващата
-пр	-ите	18 words	профилиращите, пребогатите
-пр	-ата	16 words	приложната, притежаващата
-пр	-ия	15 words	противоракетния, притежания
-пр	-то	13 words	прозводството, препострояването
-пр	-ни	9 words	производни, предхождани
-пр	-ки	7 words	прокарвайки, правейки
-пр	-на	6 words	приблизителна, престъпна

6.5 Recursive Morpheme Segmentation

Using Recursive Hierarchical Substitutability, we decompose complex words into their constituent morphemes. This approach handles nested affixes (e.g., prefix-prefix-root-suffix).

Word	Suggested Split	Confidence	Stem
пробитите	пр-обит-ите	6.0	обит
натрупванията	натрупван-ия-та	6.0	натрупван
смразяващата	смразяващ-ата	4.5	смразяващ
лишаването	лишаване-то	4.5	лишаване
телепатия	телепат-ия	4.5	телепат
плодородното	плодородно-то	4.5	плодородно
маловажното	маловажно-то	4.5	маловажно
стигналите	стигнал-ите	4.5	стигнал
латинизирани	латинизира-ни	4.5	латинизира
уругвайското	уругвайско-то	4.5	уругвайско
паразитология	паразитолог-ия	4.5	паразитолог
реализираната	реализиран-ата	4.5	реализиран
изчислимостта	изчислимост-та	4.5	изчислимост
истинностни	истинност-ни	4.5	истинност
паратаксалното	паратаксално-то	4.5	паратаксално

6.6 Linguistic Interpretation

Automated Insight: The language Bulgarian shows high morphological productivity. The subword models are significantly more efficient than word models, suggesting a rich system of affixation or compounding.

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7. Summary & Recommendations

Production Recommendations

Component	Recommended	Rationale
Tokenizer	64k BPE	Best compression (4.37x)
N-gram	2-gram	Lowest perplexity (385)
Markov	Context-4	Highest predictability (92.8%)
Embeddings	100d	Balanced semantic capture and isotropy

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Appendix: Metrics Glossary & Interpretation Guide

This section provides definitions, intuitions, and guidance for interpreting the metrics used throughout this report.

Tokenizer Metrics

Compression Ratio

Definition: The ratio of characters to tokens (chars/token). Measures how efficiently the tokenizer represents text.

Intuition: Higher compression means fewer tokens needed to represent the same text, reducing sequence lengths for downstream models. A 3x compression means ~3 characters per token on average.

What to seek: Higher is generally better for efficiency, but extremely high compression may indicate overly aggressive merging that loses morphological information.

Average Token Length (Fertility)

Definition: Mean number of characters per token produced by the tokenizer.

Intuition: Reflects the granularity of tokenization. Longer tokens capture more context but may struggle with rare words; shorter tokens are more flexible but increase sequence length.

What to seek: Balance between 2-5 characters for most languages. Arabic/morphologically-rich languages may benefit from slightly longer tokens.

Unknown Token Rate (OOV Rate)

Definition: Percentage of tokens that map to the unknown/UNK token, indicating words the tokenizer cannot represent.

Intuition: Lower OOV means better vocabulary coverage. High OOV indicates the tokenizer encounters many unseen character sequences.

What to seek: Below 1% is excellent; below 5% is acceptable. BPE tokenizers typically achieve very low OOV due to subword fallback.

N-gram Model Metrics

Perplexity

Definition: Measures how "surprised" the model is by test data. Mathematically: 2^(cross-entropy). Lower values indicate better prediction.

Intuition: If perplexity is 100, the model is as uncertain as if choosing uniformly among 100 options at each step. A perplexity of 10 means effectively choosing among 10 equally likely options.

What to seek: Lower is better. Perplexity decreases with larger n-grams (more context). Values vary widely by language and corpus size.

Entropy

Definition: Average information content (in bits) needed to encode the next token given the context. Related to perplexity: perplexity = 2^entropy.

Intuition: High entropy means high uncertainty/randomness; low entropy means predictable patterns. Natural language typically has entropy between 1-4 bits per character.

What to seek: Lower entropy indicates more predictable text patterns. Entropy should decrease as n-gram size increases.

Coverage (Top-K)

Definition: Percentage of corpus occurrences explained by the top K most frequent n-grams.

Intuition: High coverage with few patterns indicates repetitive/formulaic text; low coverage suggests diverse vocabulary usage.

What to seek: Depends on use case. For language modeling, moderate coverage (40-60% with top-1000) is typical for natural text.

Markov Chain Metrics

Average Entropy

Definition: Mean entropy across all contexts, measuring average uncertainty in next-word prediction.

Intuition: Lower entropy means the model is more confident about what comes next. Context-1 has high entropy (many possible next words); Context-4 has low entropy (few likely continuations).

What to seek: Decreasing entropy with larger context sizes. Very low entropy (<0.1) indicates highly deterministic transitions.

Branching Factor

Definition: Average number of unique next tokens observed for each context.

Intuition: High branching = many possible continuations (flexible but uncertain); low branching = few options (predictable but potentially repetitive).

What to seek: Branching factor should decrease with context size. Values near 1.0 indicate nearly deterministic chains.

Predictability

Definition: Derived metric: (1 - normalized_entropy) × 100%. Indicates how deterministic the model's predictions are.

Intuition: 100% predictability means the next word is always certain; 0% means completely random. Real text falls between these extremes.

What to seek: Higher predictability for text generation quality, but too high (>98%) may produce repetitive output.

Vocabulary & Zipf's Law Metrics

Zipf's Coefficient

Definition: The slope of the log-log plot of word frequency vs. rank. Zipf's law predicts this should be approximately -1.

Intuition: A coefficient near -1 indicates the corpus follows natural language patterns where a few words are very common and most words are rare.

What to seek: Values between -0.8 and -1.2 indicate healthy natural language distribution. Deviations may suggest domain-specific or artificial text.

R² (Coefficient of Determination)

Definition: Measures how well the linear fit explains the frequency-rank relationship. Ranges from 0 to 1.

Intuition: R² near 1.0 means the data closely follows Zipf's law; lower values indicate deviation from expected word frequency patterns.

What to seek: R² > 0.95 is excellent; > 0.99 indicates near-perfect Zipf adherence typical of large natural corpora.

Vocabulary Coverage

Definition: Cumulative percentage of corpus tokens accounted for by the top N words.

Intuition: Shows how concentrated word usage is. If top-100 words cover 50% of text, the corpus relies heavily on common words.

What to seek: Top-100 covering 30-50% is typical. Higher coverage indicates more repetitive text; lower suggests richer vocabulary.

Word Embedding Metrics

Isotropy

Definition: Measures how uniformly distributed vectors are in the embedding space. Computed as the ratio of minimum to maximum singular values.

Intuition: High isotropy (near 1.0) means vectors spread evenly in all directions; low isotropy means vectors cluster in certain directions, reducing expressiveness.

What to seek: Higher isotropy generally indicates better-quality embeddings. Values > 0.1 are reasonable; > 0.3 is good. Lower-dimensional embeddings tend to have higher isotropy.

Average Norm

Definition: Mean magnitude (L2 norm) of word vectors in the embedding space.

Intuition: Indicates the typical "length" of vectors. Consistent norms suggest stable training; high variance may indicate some words are undertrained.

What to seek: Relatively consistent norms across models. The absolute value matters less than consistency (low std deviation).

Cosine Similarity

Definition: Measures angular similarity between vectors, ranging from -1 (opposite) to 1 (identical direction).

Intuition: Words with similar meanings should have high cosine similarity. This is the standard metric for semantic relatedness in embeddings.

What to seek: Semantically related words should score > 0.5; unrelated words should be near 0. Synonyms often score > 0.7.

t-SNE Visualization

Definition: t-Distributed Stochastic Neighbor Embedding - a dimensionality reduction technique that preserves local structure for visualization.

Intuition: Clusters in t-SNE plots indicate groups of semantically related words. Spread indicates vocabulary diversity; tight clusters suggest semantic coherence.

What to seek: Meaningful clusters (e.g., numbers together, verbs together). Avoid over-interpreting distances - t-SNE preserves local, not global, structure.

General Interpretation Guidelines

1. Compare within model families: Metrics are most meaningful when comparing models of the same type (e.g., 8k vs 64k tokenizer).
2. Consider trade-offs: Better performance on one metric often comes at the cost of another (e.g., compression vs. OOV rate).
3. Context matters: Optimal values depend on downstream tasks. Text generation may prioritize different metrics than classification.
4. Corpus influence: All metrics are influenced by corpus characteristics. Wikipedia text differs from social media or literature.
5. Language-specific patterns: Morphologically rich languages (like Arabic) may show different optimal ranges than analytic languages.

Visualizations Index

Visualization	Description
Tokenizer Compression	Compression ratios by vocabulary size
Tokenizer Fertility	Average token length by vocabulary
Tokenizer OOV	Unknown token rates
Tokenizer Total Tokens	Total tokens by vocabulary
N-gram Perplexity	Perplexity by n-gram size
N-gram Entropy	Entropy by n-gram size
N-gram Coverage	Top pattern coverage
N-gram Unique	Unique n-gram counts
Markov Entropy	Entropy by context size
Markov Branching	Branching factor by context
Markov Contexts	Unique context counts
Zipf's Law	Frequency-rank distribution with fit
Vocab Frequency	Word frequency distribution
Top 20 Words	Most frequent words
Vocab Coverage	Cumulative coverage curve
Embedding Isotropy	Vector space uniformity
Embedding Norms	Vector magnitude distribution
Embedding Similarity	Word similarity heatmap
Nearest Neighbors	Similar words for key terms
t-SNE Words	2D word embedding visualization
t-SNE Sentences	2D sentence embedding visualization
Position Encoding	Encoding method comparison
Model Sizes	Storage requirements
Performance Dashboard	Comprehensive performance overview

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About This Project

Data Source

Models trained on wikipedia-monthly - a monthly snapshot of Wikipedia articles across 300+ languages.

Project

A project by Wikilangs - Open-source NLP models for every Wikipedia language.

Maintainer

Omar Kamali - Omneity Labs

Citation

If you use these models in your research, please cite:

@misc{wikilangs2025,
  author = {Kamali, Omar},
  title = {Wikilangs: Open NLP Models for Wikipedia Languages},
  year = {2025},
  doi = {10.5281/zenodo.18073153},
  publisher = {Zenodo},
  url = {https://huggingface.co/wikilangs}
  institution = {Omneity Labs}
}

License

MIT License - Free for academic and commercial use.

Links

• 🌐 Website: wikilangs.org
• 🤗 Models: huggingface.co/wikilangs
• 📊 Data: wikipedia-monthly
• 👤 Author: Omar Kamali
• 🤝 Sponsor: Featherless AI

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Generated by Wikilangs Models Pipeline

Report Date: 2026-01-07 00:49:27