Going from Azerbaijani to Persian (Farsi) (فارسی) has a composite linguistic distance of 77% (curated lexical data). Below is the dimension-by-dimension breakdown.
Shared vocabulary, cognates, and loanwords.
Morphology, syntax, word order, cases.
Shared sounds and phoneme inventory.
Latin → Arabic
Turkic ↔ Indo-European
The 5 languages with the lowest linguistic distance from Azerbaijani:
A quick 3-question check between Azerbaijani and Persian (Farsi). No signup.