A companion or partner in various contexts.

साथी

English Usage: She considered him her lifelong companion.

Hindi Usage: उसने उसे अपना जीवन भर का साथी मान लिया।

To act as a companion or associate; to accompany.

साथ देना

English Usage: He decided to companion her during the event to keep her company.

Hindi Usage: उसने घटना के दौरान उसका साथ देने का फैसला किया।