A word, such as a preposition, a conjunction, or an article, that has little semantic content of its own and chiefly indicates a grammatical relationship. Also called form word, functor.(noun)
American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.