In
phonetics, the term
aspiration means a strong burst of air accompanying the release of some
stops. English voiceless stops are aspirated when they begin a stressed syllable (as in
pen,
ten,
Ken), but this aspiration is not distinctive (they also have unaspirated variants in other positions). In many languages [t] and aspirated [t
h] (not to be confused with the English sound spelt
th as in
thin) are different
phonemes.
For example, put your hand in front of your mouth and say 'key' and then
'ski'. Key is aspirated, and ski is unaspirated.