Going from Tigrinya to Somali (Soomaali) has a composite linguistic distance of 66% (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 ↔ Afro-Asiatic
The 5 languages with the lowest linguistic distance from Tigrinya:
A quick 3-question check between Tigrinya and Somali. No signup.