so far in WordNet English dictionary

1. 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"
   so far  thus far  up to now  hitherto  heretofore  as yet  yet  til now  until now  so far  thus far  up to now  hitherto  heretofore  as yet  yet  til now  until now 
   
2. 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"
   insofar  in so far  so far  to that extent  to that degree  insofar  in so far  so far  to that extent  to that degree 
   
3. used after a superlative
   "this is the best so far"; "the largest drug bust yet"
   so far  yet  so far  yet 
   

so far in English Wiktionary