What this means for learners
NAHUATL and FIJIAN share 12 sounds — roughly 40% of FIJIAN's inventory overlaps with NAHUATL. Shared sounds are ones a speaker already knows from their native language and will generally produce and perceive accurately without explicit training.
The 18 sounds found only in FIJIAN represent the greatest pronunciation challenge for NAHUATL 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, NAHUATL has 8 sounds not used in FIJIAN. Native FIJIAN speakers learning NAHUATL 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.