1.Definition: as the agent of or on someone's part (usually expressed as `on behalf of' rather than `in behalf of')

"The guardian signed the contract on behalf of the minor child", "This letter is written on behalf of my client"

Category: General

2.Definition: for someone's benefit (usually expressed as `in behalf' rather than `on behalf' and usually with a possessive)

"In your behalf", "Campaigning in his own behalf", "Spoke a good word in his friend's behalf"

Category: General