#Obligatory and optional adverbials
Optional adverbials provide additional information. They are part of the the structure f the sentence, but they are not essential to the structure: Sometimes the children played by the lake.
Adverbials are obligatory when the sentence structure demands one or when their absence changes the meaning of the verb. This is the case:
with predicate complements:
-after to behave, to act, to treat,: He behaved bravely.
-after stratal and durative verbs(to live, to wait, to last): John lives in London.
-after verbs implying direction(to put, to and): Put the book on the shelf.
-after verbs of motion and position in space(to come,to step, to sit): He went to the dressing-room.
when an adverbial influences the meaning of a verb: I’m going to the library tomorrow.
when its absence changes the meaning of the sentence: I’ve never been there since my childhood.
From the point of view of their function, non-obligatory adverbials may be classified as adjusts, conjuncts and disjuncts.
Adjuncts(circumstance adverbials) - provide additional information and make part of the structure of the sent. Mostly: cause and consequence, sequence in time, place, manner, purpose, condition, degree of intensity.
Conjuncts (linking adverbials) - form a logical link between two clauses or sentences. Here: causal(because,therefore), temporal(finally), additive(similarly), adversative(on the other hand)
Disjunct (stance adverbials) - coming at the beginning of the sentence and expressing the speaker’s attitude towards the statement he is about to make. Here: adverbs expressing subjective or objective attitude of the speaker; expressing the speaker’s the relation of the clause with something outside it; Naturally, he likes us very much.
From the point of view of their semantics adverbials adjuncts may be identified directly(absolutely) by their lexical meaning or indirectly through the relationship of the adverbial to the modified part of the sentence, or through an identifying question