be·half
(bĭ-hăf′, -häf′)n. Interest, support, or benefit.
Idiom: on/in behalf of1. As the agent of; on the part of.
2. For the benefit of; in the interest of.
[Middle English, from Old English be healfe, by (his) side : be, by, at; see by1 + healf, side, half; see half.]
Usage Note: A traditional rule holds that in behalf of and on behalf of have distinct meanings. According to this rule, in behalf of means "for the benefit of," as in We raised money in behalf of the earthquake victims, while its counterpart on behalf of means "as the agent of, on the part of," as in The guardian signed the contract on behalf of the child. But as the two meanings are quite close, the phrases are often used interchangeably, even by reputable writers. Statistically, on behalf of is used far more frequently than in behalf of, and in fact the Usage Panel prefers on behalf of for both meanings. In our 2004 survey, 87 percent of the Panel preferred on behalf of in the sentence The lawyer spoke to the media (in behalf of/on behalf of) his client, conforming to the traditional rule for using on behalf of. But some 75 percent also preferred on behalf of in the sentence After sitting silently as one complaint after another was raised, he finally spoke up (in behalf of/on behalf of) his kid's coach, where the speaker is less of a spokesperson than an ad-hoc defender, and so the meaning "in defense of, for the benefit of" is a better fit, and the traditional rule therefore would require in behalf of. All this suggests that on behalf of may be generally supplanting in behalf of.
American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
behalf
(bɪˈhɑːf) ninterest, part, benefit, or respect (only in the phrases on (someone's) behalf, on or US and Canadian in behalf of, in this (or that) behalf)
[Old English be halfe from be by + halfe side; compare Old Norse af halfu]
Usage: On behalf of is sometimes wrongly used where on the part of is intended. The distinction is that on behalf of someone means 'for someone's benefit' or 'representing someone', while on the part of someone can be roughly paraphrased as 'by someone'. So, the following example is incorrect: another act of apparent negligence, this time not on behalf of the company itself, but on behalf of its banker, when what was meant was there was negligence by the company's banker
Collins English Dictionary – Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014
be•half
(bɪˈhæf, -ˈhɑf)
n. interest; support.
Idioms: 1. in or on behalf of, as a representative of or a proxy for.
2. in or on someone's behalf, in someone's interests.
[1400–50; late Middle English; Middle English bihalve]
Random House Kernerman Webster's College Dictionary, © 2010 K Dictionaries Ltd. Copyright 2005, 1997, 1991 by Random House, Inc. All rights reserved.