Mate (noun)

1. A close friend or companion.
2. A person with whom one has a close romantic relationship.
3. A person with whom one is married.
4. A member of a pair of birds or animals who live together and breed.
5. One of the equal members of a team in a competitive sport.

Origin:

From middle english mate, from old french mate, from latin mātus ("friend, companion"), from proto-indo-european *máhtus ("friend, companion").

Examples:

1. He and his mate have been friends since childhood.
2. The couple became mates after dating for several months.
3. After getting married, they became mates for life.
4. The pair of birds were mates for many years.
5. In soccer, the two players were mates on the same team.