It is a puff of air that gets out from the mouth with certain conditions:
- The phoneme should be plosive "stop".
- It must be voiceless /p/ , /t/ and /k/.\
- The sound must come at the beginning of the syllable.
- The syllable must be stressed.
If one of the four conditions is not applied, the aspiration does not come out. For instance, if the voiceless plosive does not come out at the beginning of the syllable, it will be another allophone called non-aspirated. Ex. spin /spɪn/ [sp=ɪn].
It is another allophone that is derived out from the vowels. It means delayed voice on set time. The pronunciation of the vowel is delayed when it comes after an aspirated allophone. It becomes offset. Ex. pin /pɪn/ [pɪ΄n] - kite /kaɪt/ [ka΄ɪt].
3- Devoiced Allophone:
Devoicing is one of the allophonic variations. It means that the voiced phoneme is pronounced with less vibration, but it does not become voiceless. Final devoicing is the first case of this allophone. It happens when a voiced phoneme comes at the end of a word followed by a pause. The voiced phoneme loses its voicing partially. Ex: bed /bed/ [bed̥] - bag [bæg̥] - some /sʌm/ [sʌm̥].
The devoiced allophone has another case like the word play /pleɪ/ [pl̥eɪ]. The voiced phoneme /l/ loses part of its voicing when it is preceded by a voiceless phoneme.
4- Dark Allophones:
The phoneme /l/ has another allophone if it is followed by certain vowels like /ʌ/ , /ɑː/ and /aɪ/. The word "less" /les/ has a clear /l/, but the word "luck" /lʌk/ has a dark [l] [Ịʌk]. Other phones like /s/, /t/, /k/ and /d/ could have dark allophones with the same conditions.
/d/ -------- /ɑː/ ------------- Dark Allophones
dark /dɑːk/ [dɑːk]
sigh /saɪ/ [saɪ]
tough /tʌf/ [tʌf]