Going from Vietnamese to Icelandic (รslenska) has a composite linguistic distance of 78% (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 โ Latin
Austroasiatic โ Indo-European
The 5 languages with the lowest linguistic distance from Vietnamese:
A quick 3-question check between Vietnamese and Icelandic. No signup.