In other words, content words give us the most important information while function words are used to stitch those words together.

Content words are usually nouns, verbs, adjectives, and adverbs. A noun tells us which object, a verb tells us about the action happening, or the state. Adjectives give us details about objects and people and adverbs tell us how, when or where something is done. Nouns, verbs, adjectives and adverbs give us important information required for understanding.

While nouns, verbs, adjectives and adverbs are the most important content words, there are a few other words that are also key to understanding. These include negatives like no, not and never; demonstrative pronouns including this, that, these and those; and question words like what, where, when, how and why.

Function Word Types

Function words help us connect important information. Function words are important for understanding, but they add little meaning beyond defining the relationship between two words. Function words include auxiliary verbs, prepositions, articles, conjunctions, and pronouns. Auxiliary verbs are used to establish the tense, prepositions show relationships in time and space, articles show us something that is specific or one of many, and pronouns refer to other nouns.

Morphemes are the smallest units of meaning in a language. They are commonly classified as either free morphemes, which can occur as separate words or bound morphemes, which can't stand alone as words.

Many words in English are made up of a single free morpheme. For example, each word in the following sentence is a distinct morpheme: "I need to go now, but you can stay." Put another way, none of the nine words in that sentence can be divided into smaller parts that are also meaningful.

While words, along with clitics, are generally accepted as being the smallest units of syntax, in most languages, if not all, many words can be related to other words by rules that collectively describe the grammar for that language. For example, English speakers recognize that the words dog and dogs are closely related, differentiated only by the plurality morpheme "-s", only found bound to noun phrases. Speakers of English, a fusional language, recognize these relations from their innate knowledge of English's rules of word formation. They infer intuitively that dog is to dogs as cat is to cats; and, in similar fashion, dog is to dog catcher as dish is to dishwasher. By contrast, Classical Chinese has very little morphology, using almost exclusively unbound morphemes ("free" morphemes) and depending on word order to convey meaning. (Most words in modern Standard Chinese ["Mandarin"], however, are compounds and most roots are bound.) These are understood as grammars that represent the morphology of the language. The rules understood by a speaker reflect specific patterns or regularities in the way words are formed from smaller units in the language they are using, and how those smaller units interact in speech. In this way, morphology is the branch of linguistics that studies patterns of word formation within and across languages and attempts to formulate rules that model the knowledge of the speakers of those languages.