What are allophones? They are all the variants of a particular sound or phoneme. Native speakers of a language are usually unaware of these variants. They use the correct ones automatically in just the right places! For example, the /p/ sound in English has several variants. At the beginning of a syllable before a stressed vowel, it is always pronounced with aspiration (a strong puff of air). We hear this allophone in words like pot, pair, particle, and oppose.
In an unstressed syllable or whenever /p/ follows /s/, the sound has no aspiration (no strong puff of air): words like potato, peculiar, spin, spot, spare, and sports.
At the end of a syllable or word, the /p/ sound may or may not be released. In other words, you might not hear any explosion of air from the lips. The unreleased allophone of /p/ is very common and occurs frequently in words like keep, stop, sleep, and laptop. It helps us to link syllables and words together. Some people who have learned English as a second language have difficulty hearing sounds like /p/ when they are unreleased. They may omit them or release them when it’s not expected.
Why are allophones so important? If you use the wrong ones when you are speaking English, listeners may hear you incorrectly. If you say “pair” without aspiration, it may sound to some English listeners like “bear.” It’s possible that your first language (if it’s not English) doesn’t ever have unreleased allophones. If you release all your final consonants, your pronunciation in English will never be as smooth as it needs to be.
Part of any good English accent training program is learning the patterns of allophones.