Morphological vs. Syntactic Inflection
We begin by distinguishing between two applications of the word inflection, one found chiefly in the morphological literature and the other in syntactic literature. For a morphologist, the presence of inflectional morphology in a language depends on the existence of multiple forms of a lexeme. If a lexeme has only one form, then there can be no morphological inflection. In syntax, there is no such requirement.
Chinese lexemes have only one form, abstracting away from phonologically determined alternations (mostly changes in tone). While Chinese has a few clitics or particles, including one that expresses past tense, these are generally not considered affixes. The same is true of Vietnamese, though the two languages are unrelated. For the morphologist, therefore, these two languages have no inflection.
From a syntactician’s point of view, whether or not Chinese and Vietnamese have inflection is an entirely different matter. Even if a language does not express a particular notion such as number or case, it is typically assumed to be present in the syntax. Likewise, a syntactician may argue that a verb always agrees with its subject in an abstract sense. This abstract agreement is considered just as real in Chinese, where the verb form never depends on its subject, as in Russian, where the form of the verb changes depending on the person (first, second, third) and number (singular or plural) of the subject. In sum, morphological inflection is realized overtly, where syntactic inflection may or may not be.
The existence of zero allomorphs does not contradict this definition of morphological inflection. Recall that we speak of zero allomorphs only if they also have non-zero allomorphs. In other words, in some instances the inflectional feature encoded by the zero allomorph is realized overtly.
Another difference between the morphological and syntactic usage of the term inflection is that morphologists speak of inflection only when dealing with bound forms. The reason for this is clear when you consider that we defined inflection informally as “bending” of a lexeme.
English has a syntactic category of modals, or modal auxiliaries. They are used to accompany other verbs and indicate that the action or state described by the sentence is something other than simple fact. Alicia might go to the birthday party isn’t a simple fact about Alicia’s going to a party; there is an element of uncertainty. If we substitute other modals for might, the degree of uncertainty changes somewhat with each substitution: Alicia may go to the birthday party; Alicia can go to the birth day party; Alicia could go to the birthday party; Alicia must go to the birthday party; Alicia should go to the birthday party; Alicia would go to the birth day party; Alicia will go to the birthday party.
Should we consider these modals to be morphological inflection? No. In order to be classified as morphological inflection, a syntactic category must be expressed through bound forms. In the case of the English modals, we are not dealing with bound forms, but rather with separate words. Again, syntacticians differ from morphologists on this point. Most would treat auxiliaries as part of the inflectional system of a language. Morphologists are not denying the validity of this treatment, only distinguishing the full-word modals (i.e., syntactic inflection) from morphological inflection.
