Going from Vietnamese to Japanese (ζ₯ζ¬θͺ) has a composite linguistic distance of 86% (heuristic estimate). Below is the dimension-by-dimension breakdown.
Shared vocabulary, cognates, and loanwords.
Morphology, syntax, word order, cases.
Shared sounds and phoneme inventory.
Latin β Japanese
Austroasiatic β Japonic
The 5 languages with the lowest linguistic distance from Vietnamese:
A quick 3-question check between Vietnamese and Japanese. No signup.