what is SO?

Excuse my ignorance but I am trying to follow these threads

Taken from http://www.merriam-webster.com/dictionary/so

"1.so adv
\ˈsō, especially before adjective or adv followed by “that” sə\

Definition of SO

1a : in a manner or way indicated or suggested —often used as a substitute for a preceding clause

b : in the same manner or way : also

c : thus 1

d : then, subsequently

2a : to an indicated or suggested extent or degree

b : to a great extent or degree : very, extremely

c : to a definite but unspecified extent or degree

d : most certainly : indeed

e : most decidedly : surely

3: therefore, consequently "