Modern grammars typically describe adverbs as the head of “adverb phrases”: adverbs may occur on their own (as in the examples above) or they may be modified by one or more dependents, themselves adverbs. While these modify the adverb head, it is the head nonetheless that is the most loaded for lexical meaning. In these examples, the head is the adverb occasionally: She tends to paint anything although occasionally a portrait > very occasionally a portrait > only very occasionally a portrait. Traditional terminology implies that adverbs are primarily verb modifiers, specifying the mode of action of the verb. Adverbs, in fact, act in a variety of ways: to modify other elements in clause structure, such as adjectives (remarkably quick), other adverbs (quite+possibly); occasionally nouns (the very top of the profession); verbs (They had completely forgotten about it); or, often, the clause as a whole (Luckily, they had some friends; It might be worthwhile actually).
Syntactically, adverbs can be related to such questions as “where?” (here, there, somewhere, nowhere); “when?” (now, tomorrow, soon); “how often?” (frequently, never twice); “how?” (well, quickly, carefully); “to what extent?” (quite, rather, fairly), and so on (Crystal, 2008, p. 14). By relating adverbs to these types of question, their functional correspondence to multiword units, called “adverbials,” soon becomes apparent. The query “When are they leaving?” might elicit: soon/tomorrow (adverb phrase, with an unmodified adverb as its head); pretty soon (adverb phrase, with the adverb soon as its head, modified by an adverb intensifier pretty); in a few days' time (prepositional phrase, with the preposition in as its head); when I see fit (finite clause). An adverbial is thus a syntactic unit, distinct from other clause elements—subject, verb, object, and complement. It is the next most frequent constituent after subject and verb (Quirk et al., 1985, p. 478n), and as Quirk et al. remark: “The vast majority of clauses . . . contain at least one adverbial” (p. 478n). When contrived data are used in sentence grammar or English‐language learning and teaching materials, this point is often ignored; adverbs are regularly omitted unless chosen for the purpose of commentary (Crystal, 1980, pp. 160–5).
Adverbs are the most mobile of all clause constituents. They enjoy greater freedom than their structurally more complex multiword counterparts, which generally favor end position. They can appear initially (I), medially (M: within the clause, in a variety of positions), and finally (E), without this affecting the grammatical acceptability of the clause: Possibly they may have been sent to Hong Kong (I); They possibly may . . . ; They may possibly . . . ; They may have possibly . . . ; They may have been possibly . . . ; They may have been sent possibly . . . (M); They may have been sent to Hong Kong possibly (E) (see Quirk et al., 1985, pp. 490–501; Huddleston & Pullum, 2002, pp. 575–8; Crystal, 2004, p. 274). Adverbs at M are more or less integrated in clause structure and restricted in their compass, whilst those at I or E tend to be peripheral—their orientation and scope affects the entire clause. Ultimately, adverb(ial) placement is often a matter of focus and stylistic choice. As Huddleston and Pullum (2002, p. 576) remark: “There is a great deal of variation in [adverb] use, and features of context, style, prosody, and euphony play a role in some decisions [on placement and focus].”
Classification
Adverbs are usually categorized according to their position and function within the clause. More than any other word class, they demonstrate the interdependency between grammar and meaning, although accounts differ markedly in their classification schemes and terminology. This may lead to terminological confusion (see Hasselgård, 2010, pp. 14–39). Quirk et al. (1985, pp. 438–653) and Crystal (2004, pp. 268–93), in his synopsis thereof, distinguish four classes of adverb divided into two main groups: adjuncts and subjuncts; disjuncts and conjuncts. Adjuncts relate to the verb or “verb phrase” (He ate slowly and surely; he had time, and he had strength) or to the entire clause (Nowadays, there is no excuse for getting into trouble). They constitute the largest subgroup of adverbs, and include such traditional categories as adverbs of place, manner, and time, sometimes known collectively as “circumstantial adverbs” (Biber et al., 1999). Occasionally, adjuncts may be obligatory—they are required by the verb to make the clause grammatically acceptable and usually occur at E: Ruth lives in Berlin; We wanted a relaxing, fun day and thankfully everything went wonderfully; The dinosaur exhibition extended through the summer (see Goldberg & Ackerman, 2001; Hasselgård, 2010, pp. 46–8, 124).
Subjuncts generally play a more subordinate role in relation either to the clause or to a clause element, especially the verb or verb phrase, here to heightening effect: We couldn't, literally couldn't, have managed without your help. Subjuncts comprise adverbs expressing: viewpoint (Economically and politically [speaking], they've been completely disenfranchised); focus (Only the lonely know the way I feel tonight); degree (You simply must let me have a copy); and courtesy, where their role is essentially formulaic (Please mind the gap / Kindly allow me to speak). In short, subjuncts add the speaker's slant toward the content of the associated clause (Crystal, 2004, pp. 284–5). Disjuncts have a superior role in relation to the clause, by making a judgment, a comment, or an evaluation about what is being said: It is arguably the most important discovery; Fortunately, or unfortunately, that is easy work now; Consequently, it is regrettably inevitable that personal property will occasionally go missing. Conjuncts are peripheral to clause structure and have a linking or relational function between clauses when these are viewed as connected discourse: It happened before dawn so they might have been asleep at the time; Environment can never completely explain art. I am sure, however, that it plays an important role; We have a way of talking, and thus a way of thinking. In combination with modal verbs, certain types of subjunct and disjunct are significant for the expression of modality: In this context it may well be true; This is one wheel that you definitely should not try to reinvent; Perhaps they might even learn to think critically instead of parroting; Of course, there may be special occasions where an exception should be made. (See further Hoye, 1997; see also Simon‐Vandenbergen & Aijmer, 2007, pp. 68–9, and Aijmer, 2009, on the issue of modal adverbs and modal particles.)
Semantic Roles
Since adverbs express such a wide range of meanings, treatment of their grammar also involves focusing on their semantic roles. Quirk et al. (1985, pp. 479–86) distinguish seven broad categories, often based on a figurative extension of what they call “spatial relations,” and with a clear nod to the traditional categories of time, place, manner, frequency, and degree, although more rigorously articulated. Space or “place” adverbs refer to position (Change here), direction (They were speeding southward), distance (It's