How do you change the word 'work' into 'play' by changing one letter at a time to spell a different word?

Four solutions (by size):

6 steps:

work

pork

perk

peak

peat

plat

play

7 steps:

work

cork

cook

coot

clot

plot

ploy

play

9 steps:

work

fork

fort

fart

fast

fist

Fiat

flat

flay

play

10 steps:

work

pork

port

pert

peat

seat

sear

star

stay

slay

play