Going from Arabic (MSA) to Persian (Farsi) (فارسی) has a composite linguistic distance of 70% (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.
Arabic → Arabic
Afro-Asiatic ↔ Indo-European
The 5 languages with the lowest linguistic distance from Arabic (MSA):
A quick 3-question check between Arabic (MSA) and Persian (Farsi). No signup.