almost vs well-nigh

almost and well-nigh both are adverbs.

Word	Noun	Adjective	Verb	Adverb
almost	No	No	No	Yes
well-nigh	No	No	No	Yes

As adverbs, almost and well-nigh are synonyms defined as:

almost and well-nigh: (of actions or states) slightly short of or not quite accomplished; all but

Other synonyms of almost include about, most, near, nearly, nigh, virtually.

almost (adverb)	well-nigh (adverb)
(of actions or states) slightly short of or not quite accomplished; all but	(of actions or states) slightly short of or not quite accomplished; all but