From Teflpedia

So (/səʊ/) is an English word that functions as a conjunction, an adjective, an adverb or an interjection.[1]

So can be used to introduce a result clause, e.g. "I like beans, so I eat them every day." Its antonym is because.

So can be used for negative similes; "not so... as..."

It can be reduced as a weak form to /sə/.

It has a true friend in other Germanic languages, e.g. German "so", Dutch "zo", Danish/Swedish så

So is a homophone with the verb sew.