What this means for learners
SOCOTRI and TETUN share 17 sounds — roughly 50% of TETUN's inventory overlaps with SOCOTRI. Shared sounds are ones a speaker already knows from their native language and will generally produce and perceive accurately without explicit training.
The 2 sounds found only in TETUN represent the greatest pronunciation challenge for SOCOTRI speakers. The adult brain tends to map unfamiliar sounds onto the closest native equivalent — a process that produces the characteristic "accent" of a second-language speaker. Learning to hear and produce these sounds as distinct requires focused ear training, not just repetition.
Conversely, SOCOTRI has 17 sounds not used in TETUN. Native TETUN speakers learning SOCOTRI will face the mirror-image challenge with these sounds.
Phoneme inventories from PHOIBLE. Data reflects one documented inventory per language; some variation exists across dialects and sources.