I can'r figure out. While modifiers are optional, complements are obligatory, they cannot be left out. Small Phrase Layers: A study of Finnish Manner Adverbials | Satu … complements). How to use "obligatory" in a sentence NEU von Collins! NUMBER106 OCTOBER2016 5–20 - cuni.cz When used as adjectives, obligatory means imposing obligation, legally or morally, whereas optional means not compulsory. Linguistic Valency in English Grammar - ThoughtCo In (5), a simplex wh-complement 何 he fronts out of a head-initial PP 為何 wei he ‘for what’ that functions as an adverbial of reason above negation, generating the inverted wh-P order. 1. trasts with other word classes, such as nouns, adjectives, verbs, or prepositions. Arguments for distinguishing complements from modifiers (OPTIONAL) As I mentioned in section 2, inside the NP, some elements are more closely related to the head N than others. Optional And Obligatory Adverbials. - englishforums.com The difference in function between (obligatory) complements of the verb and (optional, modifying) adjunct adverbials is to be represented in phrase markers as follows: Complements of the verb are sisters of Verb (V).