If there is a small puff of air following a speech sound, it is called aspiration. The /p/ sound, for instance, is often aspirated when it comes at the beginning of a word, like /pɪn/, but the is no aspiration if it comes after /s/, as in /spɪn/.
'Aspiration' - Related Links
Grammar Topic: Pronunciation
Browse the following links to other content related to 'Aspiration' from the 'Pronunciation' grammar category: