Lexical and Functional Meaning

A morpheme is a meaningful linguistic unit, and morphemes fall into two broad kinds that must be analyzed with different tools. A functional morpheme is a meaningful grammatical element that usually has a logical meaning and belongs to the grammar of a language. A lexical morpheme is a meaningful lexical element that usually has an abstract meaning, including at least some components that cannot be logically represented, and belongs to the lexicon.

In the sentence the bear escaped from the zoo, the two kinds sit side by side. The, the -ed suffix on escape, and from are functional morphemes; bear, escape, and zoo are lexical morphemes. Prepositions are a debated category, listed here with the functional morphemes.

Contrasting Characteristics

The two kinds differ in meaning type. Functional morphemes have logical meanings: the past-tense -ed can be given the crude logical definition "the event happens before the statement is made," and a logical formula can be built using symbols for temporal precedence. Even the is standardly given a logical definition. Lexical morphemes, by contrast, have at least some components that cannot be represented logically. It is very hard to claim that every component of the meaning of bear can be captured logically.

They also differ in inventory. Functional morphemes form a closed class: languages have relatively few of them, and new ones develop only slowly, through a process called grammaticalization. Lexical morphemes form an effectively unlimited, open class; new words are coined freely as new things appear. Google, for instance, was not a verb twenty-five years ago, but once the search engine became widely used, people quickly began saying it as a verb.

Some examples of functional morphemes are gender, number, and determiners (with nouns); tense, aspect, and modality (with verbs); degree words (with adjectives); wh-elements such as who, what, where, when, why; and negation. Lexical morphemes are the verbs, nouns, adjectives, and adverbs.

Why the Difference Matters for Analysis

Lexical meanings are notorious for having fuzzy boundaries. Ludwig Wittgenstein famously argued that no precise definition could be given for the word game, since some things may or may not count as games. Functional morphemes do not behave this way.

This forces different methods. The -ed suffix can be defined simply as a temporal relationship between two intervals. A word like escape resists such treatment. One might say escape means moving from one location to another, which is true, but that also describes go; there is something in escape absent from go that a change-of-location formula does not exhaust. Because the full meaning of escape cannot be captured logically, it calls for lexical semantics, whereas the logical meanings of functional morphemes are the province of formal semantics. This roughly tracks the divide between cognitive linguistics, which has focused more on lexical semantics, and generative linguistics, whose semanticists have focused more on formal semantics, though there has been substantial crossover in both directions.