The intensive use of so (sense 2b) is widely condemned in college handbooks but is nonetheless standard <why is American television so shallow? — Anthony Lewis><the cephalopod eye is an example of a remarkable evolutionary parallel because it is so like the eye of a vertebrate — Sarah F. Robbins><the kind of sterile over-ingenuity which afflicts so many academic efforts — Times Literary Supplement>. There is no stigma attached to its use in negative contexts and when qualified by a dependent clause <not so long ago><was so good in mathematics that he began to consider engineering — Current Biography>. The denotation in these uses is, of course, slightly different (see sense 2a). Another emphatic use of so (sense 2e) has developed more recently and occurs mostly in informal contexts.
—used in speech to introduce a statement or question
Full Definition of SO
a: with the result that <the acoustics are good, so every note is clear>
b: in order that <be quiet so he can sleep>
archaic: provided that
a: for that reason :therefore<don't want to go, so I won't>
b (1) —used as an introductory particle <so here we are> often to belittle a point under discussion <so what?>(2) —used interjectionally to indicate awareness of a discovery <so, that's who did it> or surprised dissent