Based on their meaning, adverbials can be divided into different types.
ADJUNCTS add information about the event, state, etc. denoted by the clause with respect to such circumstances as, place, time, manner, reason, means, condition, etc. They thus provide information about where, when, how, or why, for instance, an event occurred. This is by far the largest and most common class of adverbials.
DISJUNCTS add information not directly related to the state, event, etc. expressed by the clause. Rather, they are used to express, for instance, the speaker's attitude to the content of the clause, somebody's evaluation of the likelihood, possibility, probability, etc. that the message is true.
CONJUNCTS express how the clause relates to the context, for instance to the previous clause in a text. Many logical or rhetorical relations are expressed by conjuncts, such as order (firstly, secondly, etc.), contrast (however, despite this, etc.), and addition (in addition, moreover, etc.).
As disjuncts and conjuncts are particularly relevant to academic writing, we pay special attention to them here.
Disjuncts can be divided into different kinds depending on what type of perspective they offer on the content of the clause.
MODAL DISJUNCTS provide information about the certainty, limitations, and sources of the content of the clause. As the name suggests, in terms of meaning, they are similar to modal auxiliary verbs, and sometimes either a construction with a modal auxiliary or one with a modal disjunct can be used to convey the same meaning. Compare the following pair of sentences.
(1) The results may have been affected by the design of the experiment.
(2) Maybe/Perhaps the design of the experiment affected the results.
Here, the first sentence uses a modal auxiliary to express the likelihood of the results having been affected by the design of the experiment, whereas the second sentence uses a modal disjunct (maybe or perhaps).
The following table lists some modal disjuncts along with definitions from the Oxford English Dictionary and some examples of their use.
arguably 'as may be shown by argument or made a matter of argument'
(3) Such norms arguably differ from the rules which copyright law allows publishers to enforce.
certainly 'without fail, unfailingly, infallibly'
(4) Such repeated exposure would certainly allow the company to attract more capital.
undoubtedly 'without or beyond any doubt'
(5) Yoga has undoubtedly contributed to his improvement.
apparently 'so far as it appears from the evidence; so far as one can judge'
(6) Apparently, no attempt was made to protect the city.
in fact 'in reality'
(7) Most of these questions have been approached in very traditional ways. In fact, 95% of the studies published in the 1990s used some form of reductionist method.
In terms of meaning, modal disjuncts may be further subdivided. Thus, we may distinguish the following types (the examples given are mostly adverbs, but other forms (prepositional phrases, clauses) can also be used:
Expressing certainty or conviction
certainly, clearly, decidedly, definitely, indisputably, surely, unarguably, undeniably, unquestionably
Expressing some degree of doubt or contrast with reality
arguably, conceivably, (quite) likely, seemingly, hypothetically, ideally, nominally, superficially, technically, theoretically
Attributing claims to sources of knowledge
allegedly, apparently, evidently, reportedly, reputedly, according to X
ATTITUDINAL DISJUNCTS - convey the speaker/writer's evaluation of what is said. Among the wide range of evaluations or value judgements that we can make, some are more important to academic writing than others. For example, it is often relevant to pass judgments in terms of whether something is right or wrong, expected or unexpected, preferable, etc. The following examples illustrate the use of disjuncts to evaluate content in such terms.
(8) Weiner (1945) correctly claims that Frege believed that knowledge is language dependent.
(9) Smith (2001) incorrectly claims that nothing was done to stop the spread of malaria in the first few months after the flood.
(10) The first results unexpectedly showed that the veins were, in fact, visible when infrared photography was used.
(11) Predictably, more striking results were obtained when the mice were subjected to repeated exposure over several days.
(12) Preferably, such interference should be kept to minimum to avoid contamination of the data.
Conjuncts (Linking adverbials)
Conjuncts, or linking adverbials, serve to link independent units to other elements in the text. The prototypical conjunct links one sentence to another, preceding one.
Moreover, conjuncts explicitly indicate how the second sentence should be understood in relation to the first one. Conjuncts are, therefore, essential in the creation of complex texts, where it is important to help the reader understand e.g. the logical structure of an argument.
Using simple adverb phrases, the following examples illustrate the use of conjuncts to connect a sentence to the preceding context. (A useful exercise to understand the importance of conjuncts would be to remove them from the text and see how its intelligibility deteriorates).
(13) To avoid 'leakage', i.e. the spilling over of sound into other open microphones, isolating baffles may be placed strategically in the room. Alternatively, instruments may be placed in separate rooms, or in isolated booths. However, the latter method makes communication between the musicians more difficult. Consequently, recordings of improvised musical genres like jazz tend to prefer the option of keeping all the musicians in the same room.
As is clear from this example, conjuncts encode many different kind of relations between the clause they introduce and the surrounding context. Here, we present a few classes of conjuncts (mostly in the form of simple adverb phrases) based on the type of relation they have to the context.
Additive conjuncts (roughly 'the following clause is an addition to the preceding text')
again, also, furthermore, moreover, in addition
Resultative conjuncts (roughly 'the following clause encodes the result of the preceding text')
consequently, hence, thus, as a result
Contrastive conjuncts (Roughly 'the following clause is in contrast with the preceding text')
conversely, in contrast, on the other hand, however, nevertheless, on the other hand
Listing conjuncts (indicate the sequential position of a sentence with respect to the context)
first(ly), second(ly), to begin with, next, finally, last(ly)