Say banana. If your last syllable is a strong "AH" (banan-AH), you sound less natural than you could. In English, a single A at the end of a word is almost always the tiny, relaxed schwa /ə/, the "uh" sound. So it is buh-NAN-uh, SO-fuh, DRAH-muh.
This one habit change makes hundreds of common words instantly sound native.
The Rule
When a word ends in a single, unstressed A, pronounce it as schwa /ə/, never as a full /a/ or /eɪ/. This is the same lazy vowel at the start of about and around. It applies to a huge family of words: banana, sofa, drama, camera, America, idea, extra, comma, panda, pizza, data, area, opera, umbrella, formula, agenda. Your mouth should barely move: relax the jaw, let the sound fall to a soft "uh," and stop.
Practice Words
When Final A Is Not Schwa
The schwa rule needs the final A to be unstressed. In short, one-syllable words the A carries the stress and stays a full /ɑː/: spa, bra, ma, pa, ha. A few borrowed words also keep a strong final vowel when that syllable is stressed. But for the everyday multi-syllable words above, the ending is always the quiet "uh." When in doubt with a long word, reduce the last A rather than stress it.
Quick Tip
Read this chain out loud, keeping every final A soft and equal: a banana, a sofa, a camera, an idea, an umbrella, an agenda. If each one ends in the same little "uh," you have the rule.