so far

adverb

1. used in negative statement to describe a situation that has existed up to this point or up to the present time

   adv.all

   Examples

   So far he hasn't called.

   Source: WordNet 3.0

2. to the degree or extent that

   adv.all

   Examples

   So far as it is reasonably practical he should practice restraint.

   Source: WordNet 3.0

3. used after a superlative

   adv.all

   Examples

   This is the best so far.

   Source: WordNet 3.0