What are the differences between: yet/even though; so/because; though/although?

I'll do my best to show the differences between the two words/phrases in each set. The way I'll do it is to have an example sentence using each, then highlight the differences in the two words/phrases.

• Yet vs. Even though

Example with "yet"

She was given a warning, and yet she persisted.

Example with "even though"

Even though she was given a warning, she persisted.

The emphasis between "yet" and "even though" is to highlight the conditions of action and reactions and/or consequences. With "yet", we're highlighting the reaction - the fact that "she persisted". With "even though", we're highlighting the action - in this case, the warning.

• So vs Because

Example with "so"

Our car needed a new muffler and so we took it to the garage to be repaired.

Example with "because"

Because our car needed a new muffler, we took it to the garage to be repaired.

This is very similar to the above "yet vs even though" usage, but here we're talking about reasons for doing things and the actions taken because of those actions (vs the negative connotation of both "yet" and "even though").

"So" focuses on the action taken while "because" focuses on the reason for the action.

• Though vs Although

Example with "though"

Bob decided to buy the used 2011 Corolla though he really like the thought of buying a new car.

Example with "although"

Although Bob liked the idea of buying a new car, he decided to buy the used Corolla.

"Though" is used in a parenthetical manner. We could have said in that first example: Bob decided to buy the used 2011 Corolla (but he really like the thought of buying a new car.), but we opted to use "though". "Although" does the same sort of thing but carries a bit more weight - you can see Bob in that second example very nearly buying the new car while in the first example he's only dreaming about the new car.