Real Dictionary

s.o. in American English
abbreviation: seller's option
abbreviation: Signal Officer

S.O. in British English
abbreviation for: strike out

so
You use so to refer back to something that has just been mentioned.

SO in American English
strikeout(s)

so in American English 1
in the way or manner shown, expressed, indicated, understood, etc.; as stated or described; in such a manner
adverb: in the way or manner indicated, described, or implied

so in American English 2
sol2
noun

so in American English 3
south

SO in British English
abbreviation for: significant other: often used in social media

so in British English 1
adverb: to such an extent

so in British English 2
noun

so in British English 3
the internet domain name for: Somalia

So. in American English
abbreviation: South