Function words (or grammatical words or synsemantic words or structure-class words) are words that have little lexical meaning or have ambiguous meaning, but instead serve to express grammatical relationships with other words within a sentence, or specify the attitude or mood of the speaker. They signal the structural relationships that words have to one another and are the glue that holds sentences together. Thus, they serve as important elements to the structures of sentences. [1] Consider the following two sentences:
1. The winfy prunkilmonger from the glidgement mominkled and brangified all his levensers vederously.
2. Glop angry investigator larm blonk government harassed gerfritz infuriated sutbor pumrog listeners thoroughly.
In sentence (1) above, the content words have been changed into nonsense syllables but it is not difficult for one to posit that winfy is an adjective, prunkilmonger, glidgement, levensers as nouns, mominkled, brangified as verbs and vederously as an adverb based on clues like the derivational and inflectional morphemes. (The clue is in the suffixes: -y indicates adjectives such as "wintery"; -er, -ment and -ers indicates nouns such as "baker", "battlement" and "messengers"; -led and -fied suggests verbs such as "mingled" and "clarified"; and -ly is that of adverbs such as "vigorously"). Hence, even without lexical meaning, the sentence can be said to be rather "meaningful". However, when the reverse is done and the function words are being changed to nonsense syllables as in sentence (2), the result is a totally incomprehensible sentence as the grammatical meaning which is signaled by the structure words is not present. Hence, function words provide the grammatical relationships between the open class words and helps create meaning in sentences.
Words that are not function words are called content words (or open class words or lexical words or autosemantic words): these include nouns, verbs, adjectives, and most
References: Main article: sound change This section requires expansion.(September 2010)