A partner is a person who is involved with one or more others in a common interest. In business partners may refer to members of professional practice or those who run and finance a company. A silent partner or a sleeping partner refers to someone who has made an investment in the business and shares the profits but takes no part in the day-to-day management.
Partner is sometimes used as a synonym for a husband or a wife but nowadays also includes couples who cohabit out of wedlock or in a same-sex marriage.
In sports and games a partner is one of a pair who play together as a team; e.g. tennis, bowling, or bridge.
When two people dance together, such as in ballroom dancing or ballet then they are also known as dance-partners.