so as an adverb

As an adverb, so is used mainly with the following meanings:

• as a modifier meaning “to such a degree, to a great degree,” before other modifiers or with a verb
  • Karla dances so lightly and gracefully.
  • The watch was so expensive that Juan was afraid to wear it.
  • Al loves his children so.
• as a modifier meaning “as previously described,” after a verb
  • I don’t know for sure if Maria’s going, but I think so.
  • The weather is not too hot, but with the humidity, it seems so.
• as a modifier meaning “as described, to the same degree, also” before an inverted subject and verb
  • Michel said he would win, and so he did.
  • My sister wants to leave on Wednesday, and so do I.

More recently, so has come to be used as an intensifier, similar to definitely. Such uses have been called the “Gen X so”:

• Your shirt is so eighties.
• We so aren’t going to Calgary.
• It is so not my problem.

The Gen X so is considered slang and should be avoided in formal writing and speech.