adverbs
used in negative statement to describe a situation that has existed up to this point or up to the present time
"So far he hasn't called"; "the sun isn't up yet"
to the degree or extent that
"insofar as it can be ascertained, the horse lung is comparable to that of man"; "so far as it is reasonably practical he should practice restraint"
used after a superlative
"this is the best so far"; "the largest drug bust yet"