approximately vs just about

approximately and just about both are adverbs.

Word	Noun	Adjective	Verb	Adverb
approximately	No	No	No	Yes
just about	No	No	No	Yes

As adverbs, approximately and just about are synonyms defined as:

approximately and just about: (of quantities) imprecise but fairly close to correct

Other synonyms of approximately include about, around, close to, more or less, or so, roughly, some.

approximately (adverb)	just about (adverb)
(of quantities) imprecise but fairly close to correct	(of quantities) imprecise but fairly close to correct