frequent vs buy at

frequent is an adjective but buy at is not an adjective.

Word	Noun	Adjective	Verb	Adverb
frequent	No	Yes	Yes	No
buy at	No	No	Yes	No

As verbs, frequent and buy at are synonyms defined as:

frequent and buy at: do one's shopping at; do business with; be a customer or client of

Other synonyms of frequent include patronise, patronize, shop, shop at, sponsor.

frequent (adjective)	buy at (adjective)
coming at short intervals or habitually
frequently encountered

frequent (verb)	buy at (verb)
be a regular or frequent visitor to a certain place	do one's shopping at; do business with; be a customer or client of
do one's shopping at; do business with; be a customer or client of