feint, feisty, fenny, fine, finite, infest, inset, nest, nine, ninety, nisei, nite, seif, seniti, sennit, sent, sine, sinnet, site, stein, stye, syne, tein, tennis, tine, tinnie, yeti
intensify is the word using all the letters.
I got 17 of these, Susan, and also "nite" which I assumed didn’t count but I see it does!
Glad you are enjoying Sudoku. I highly recommend Wayne Gould’s site, see the sidebar of Petrona for the link. Wayne is the person who bought Sudoku to the UK in November 2004, his website has a free trial and then for a very reasonable price (about 15 US dollars I think) you can buy his interactive puzzle and never run out again! (You can set your own level also). Much imitated since, but he’s the original (out of Japan).