Restful means making you feel calm and rested. A restful room, a restful holiday, restful colours.
It describes what produces rest rather than what is resting, which is the whole distinction from restive — restive means unable to keep still and is nearly the opposite, though the two are confused constantly. Restful colours are muted ones. Note restfully; and that a restful night's sleep is one of the commonest phrases the word appears in.
1adjectiverestfulMaking you feel calm and rested.
“We spent a restful weekend in the countryside, reading books and sleeping late.”
restful is a quality of calm.
Middle English restful is rest plus -ful. Restive comes from a different route, through French, and originally meant refusing to move — which is why it means the opposite of what it looks like.
Middle English
restful
English, today
restful
From Middle English restful, restfulle, equivalent to rest + ful.
Etymology from Wiktionary, CC BY-SA