The Most Similar Languages to Polish

Polish is an Indo-European language, primarily spoken in Poland. Many languages in the Slavic branch of the family are extremely similar to it. According to the eLinguistics.net analysis using specific software modules to assess linguistic relationships, the five languages most similar to Polish are Serbian, Slovak, Ukrainian, Slovene, and Russian.

1. Serbian (92.6)
   Polish and Serbian share some old Slavic vocabulary. However, Polish phonology (especially nasal vowels) and spelling can be a challenge for Serbian speakers. Grammar is similar in complexity, but word endings and conjugation patterns often differ. Still, a Serbian speaker might pick up on certain words or phrases due to shared etymology.
2. Slovak (92.5)
   As a fellow West Slavic language, Slovak is perhaps the most naturally similar to Polish. The two languages share nearly identical grammatical structures, a large percentage of common vocabulary, and similar pronunciation patterns. Mutual intelligibility between Polish and Slovak speakers is relatively high, particularly in spoken forms.
3. Ukrainian (92.2)
   Ukraine borders Poland, so it is not surprising Ukrainian is on this list too. Ukrainian exhibits a strong degree of similarity to Polish due to historical contact, especially during the time of the Polish-Lithuanian Commonwealth. Although Ukrainian uses the Cyrillic script, its vocabulary includes many loanwords from Polish.
4. Slovene (91.9)
   Slovene is a South Slavic language, but still retains many linguistic elements that are familiar to Polish speakers. Vocabulary overlap, similar noun cases, and shared verb aspects contribute to the linguistic closeness. However, mutual intelligibility is not as high as with other languages on this list.
5. Russian (91.6)
   As the largest and most widely spoken Slavic language, Russian is part of the East Slavic group. There remains a significant overlap in core vocabulary and grammatical concepts in Russian and Polish. Additionally, many Polish speakers study Russian as a second language, and vice versa, further enhancing cross-linguistic understanding.

(to be considered for the list, the language must be spoken by at least one million people)