The letter "A" is an example of a vowel.
Origin of vowel
- Middle English vowelle from Old French vouel from Latin (littera) vōcālis sounding (letter) from vōx vōc- voice wekw- in Indo-European roots
From American Heritage Dictionary of the English Language, 5th Edition
- From Old French vouel (French: voyelle), from Latin vōcālis (“voiced").