Auxiliaries
Authors: Bjorkman Bronwyn M. 
Published: June 2013

It is impossible to provide a definition of “auxiliary” that is consistent with all of its uses in the literature, but the term is most often used to refer to elements that express (or are involved in the expression of) clause-level distinctions such as tense, aspect, mood, modality, voice, agreement, polarity, and evidentiality. “Auxiliary” is thus sometimes used interchangeably with “auxiliary verb” (occasionally “helping verb”), as such inflectional auxiliaries must generally co-occur with a main (lexical) verb and typically bear finite inflection whereas the main verb occurs in a nonfinite or participial form (though other patterns are possible). In some work, however, auxiliaries are understood to include uninflected particles that do not morphologically resemble verbs—this definitional question is addressed most directly in typological work on Grammaticalization, as well as in the AUX versus Main Verb Debate in the generative tradition. The works cited here focus on auxiliary verbs that co-occur with main verb predicates (excluding both copulas and inflectional particles), though exceptions are noted where relevant. Auxiliaries are also often discussed under the heading of “periphrasis.” Though this more general term applies to any case in which a category is expressed syntactically rather than morphologically (as in the periphrastic comparative more beautiful rather than beautiful-er), in practice it is often used to refer only to verbal periphrasis. Auxiliaries have been the focus of much work on grammaticalization, as they often develop from main verbs (particularly predicational and copular verbs, verbs of possession, and verbs of motion and position), and related work in historical linguistics charting the development of auxiliary verbs in particular languages. Within recent work in generative theoretical linguistics, auxiliaries have been used as a diagnostic window into issues such as clause structure and verbal inflection, and within the Principles and Parameters tradition they have contributed to investigations of head movement, though auxiliaries have rarely been the central focus of recent work in this tradition. Auxiliaries have been the focus of some work in language acquisition, again often as a diagnostic of broader acquisition of clause structure and tense/aspect systems. In the generative tradition, much syntactic and semantic work on auxiliaries has focused on auxiliaries such as be and have and on modal auxiliaries (the latter particularly in formal semantics) and their distinctive syntactic properties in English (and, to some extent, related European languages). More “lexical” auxiliaries, such as those derived from verbs of motion, lack these properties and have received much less attention in this tradition. Work on typology and grammaticalization, by contrast, has typically focused on a much broader range of auxiliary verbs, as have works describing in detail the auxiliary systems of particular languages. This broader focus better captures the morpho-semantic characterization of auxiliaries, given at the beginning of this article, as lexical elements that express categories typical of inflection. Many of the works cited here do mainly discuss English and related languages, reflecting the focus of much theoretical work in linguistics. Exceptions are noted where relevant.