ablaut vs vowel

ablaut and vowel both are nouns.

Word	Noun	Adjective	Verb	Adverb
ablaut	Yes	No	No	No
vowel	Yes	No	No	No

As nouns, vowel is a hypernym of ablaut; that is, vowel is a word with a broader meaning than ablaut:

ablaut: a vowel whose quality or length is changed to indicate linguistic distinctions (such as sing sang sung song)
vowel: a speech sound made with the vocal tract open

Other hypernyms of ablaut include vowel sound.

ablaut (noun)	vowel (noun)
a vowel whose quality or length is changed to indicate linguistic distinctions (such as sing sang sung song)	a speech sound made with the vocal tract open
	a letter of the alphabet standing for a spoken vowel