Behalf means speaking or acting for someone. A parent can sign forms on behalf of children when they are young, but adult children can sign on behalf of their aging parents.

Some people make a distinction between the meaning of the word behalf when paired with in versus on. In behalf, they argue, is used when the meaning is in the interest of someone else, but on behalf is used when speaking for someone. For example, a medical decision would be made in behalf of the patient, and you would speak on behalf of your family. The reality is that on behalf is typically used for both meanings.

Definitions of behalf
  1. noun
    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”
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    type of:
    lieu, place, position, stead
    the post or function properly or customarily occupied or served by another
  2. noun
    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
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    type of:
    interest, sake
    a reason for wanting something done
Word Family

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