6 letter word: I E S T I R

3 letter words
Its
Pet
Pie
Pis (plural of pi - 3.147)
Pit
Psi
Set
Sip
Sit
Tie
Tip

4 letter words
Pest
Pets
Pies
Pits
Site
Spit
Step
Ties
Tipi
Tips

5 letter words
Piste - strip on which two people fence
Spite

6 letter words
Pities