Seven
Part of speech: noun
Definition: The digit/figure 7 or an occurrence thereof. A card bearing seven pips.
Part of speech: numeral
Definition: The cardinal number occurring after six and before eight; 7.
Example sentence: I have four kids, seven grandkids, and four great-grandkids. Maybe I can become a great-great-grandfather if I hang on!
Septet
Part of speech: noun
Definition: A group of seven; often applied to a musical group of seven performers.