What this means for learners
MOR and TETUN share 13 sounds — roughly 68% of TETUN's inventory overlaps with MOR. Shared sounds are ones a speaker already knows from their native language and will generally produce and perceive accurately without explicit training.
The 6 sounds found only in TETUN represent the greatest pronunciation challenge for MOR 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, MOR has 6 sounds not used in TETUN. Native TETUN speakers learning MOR 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.