fast vs abstain

fast is a noun but abstain is not a noun.

Word	Noun	Adjective	Verb	Adverb
fast	Yes	Yes	Yes	Yes
abstain	No	No	Yes	No

As verbs, abstain is a hypernym of fast; that is, abstain is a word with a broader meaning than fast:

Other hypernyms of fast include desist, refrain.

As verbs, abstain is a hypernym of fast; that is, abstain is a word with a broader meaning than fast:

Other hypernyms of fast include desist, refrain.

fast (noun)	abstain (noun)
abstaining from food

fast (adjective)	abstain (adjective)
acting or moving or capable of acting or moving quickly
at a rapid tempo
(used of timepieces) indicating a time ahead of or later than the correct time
(of a photographic lens or emulsion) causing a shortening of exposure time
unwavering in devotion to friend or vow or cause
securely fixed in place
hurried and brief
unrestrained by convention or morality
resistant to destruction or fading
(of surfaces) conducive to rapid speeds

fast (verb)	abstain (verb)
abstain from eating	choose not to consume
abstain from certain foods, as for religious or medical reasons	refrain from voting

fast (adverb)	abstain (adverb)
quickly or rapidly (often used as a combining form)
firmly or closely