Very similar words

driver, drive, drives, driving
sleeper, sleep, sleeps, sleeping
murderer, murder, murders, murdering
catcher, catch, catches, catching
programmer, code, codes, coding
chef, cook, cooks, cooking
killer, kill, kills, killing
bird, chirp, chirps, chirping
kisser, kiss, kisses, kissing
hugger, hug, hugs, hugging
toucher, touch, touches, touching