Yes, yet is a Scrabble word!
...and is worth 6 points in Scrabble, and 5 points in Words with Friends
yet
Adverb
1. Up to the present time
2. Used in negative statement to describe a situation that has existed up to this point or up to the present time
3. To a greater degree or extent; used with comparisons
4. Within an indefinite time or at an unspecified future time
5. Used after a superlative
6. Despite anything to the contrary (usually following a concession)
What Scrabble words can I make with the letters in yet?
3 Letter Words
2 Letter Words