This term is confusing. In traditional Gaelic grammar aspiration is refers to the phenomenon of lenition. This is not the standard usage among grammarians today, who reserve the term aspiration for the phonetic phenomenon described below involving a puff of air when pronouncing a consonant. In this wiki we will use the term aspiration only for this latter phonetic usage. The initial consonant mutation, indicated orthographically by writing an <h> after the letter, but not actually involving the phonetic phenomenon of aspiration will only be called lenition.
The Phonological Phenomenon Of Aspiration
Aspiration in Onset Position
Aspiration in Coda Position (preaspiration)
See the article Preaspiration