Going from Amharic to Swahili (Kiswahili) has a composite linguistic distance of 89% (heuristic estimate). Below is the dimension-by-dimension breakdown.
Shared vocabulary, cognates, and loanwords.
Morphology, syntax, word order, cases.
Shared sounds and phoneme inventory.
Ge'ez → Latin
Afro-Asiatic ↔ Niger-Congo
The 5 languages with the lowest linguistic distance from Amharic:
A quick 3-question check between Amharic and Swahili. No signup.