| car | cars | scar | cartoon | cardboard | carnivore |
| star | stars | starting | started | starring | starvation |
| door | doors | doormat | doorbell | doorstop | doorknob |
| floor | floors | floored | flooring | floorboard | floorboards |
| fur | furs | further | furry | furniture | furthermore |
| hurt | hurts | hurting | hurtled | hurtful | hurtfully |
| stir | stirs | stirred | stirrer | stirring | stirringly |
| firm | firms | firmly | firmer | firmest | infirmary |
