seven

Concise Oxford English Dictionary © 2008 Oxford University Press:
seven/ˈsevn/

▶cardinal number

• 1 equivalent to the sum of three and four; one more than six, or three less than ten; 7. (Roman numeral: vii or VII)

• 2 (sevens) seven-a-side rugby.

– phrases
the seven deadly sins (in Christian tradition) the sins of pride, covetousness, lust, anger, gluttony, envy, and sloth.
the seven seas all the oceans of the world (conventionally the Arctic, Antarctic, North Pacific, South Pacific, North Atlantic, South Atlantic, and Indian oceans).
the Seven Wonders of the World the seven most spectacular man-made structures of the ancient world.
the seven-year itch a supposed tendency to infidelity after seven years of marriage.

– derivatives
sevenfold adjective & adverb.

– origin OE seofon, of Gmc origin.