Adverbs are words that modify verbs, nominal predicates, adjectives, other adverbials, or whole sentences. 'Adverbial' is a broader term used to cover all types of sentence constituent that perform the function of an adverb. Adverbials vary widely in structure, from single words through noun phrases, with or without suffixes and postpositional phrases. Many lexical items whose primary function is adjectival can be made to function adverbially simply by placing them in the immediately preverbal position. Certain adverbials are formed by the reduplicated use of a noun, adjective or adverb. Adverbial clauses are the most complex kinds of adverbial construction. Some types of adverbial meaning, such as reason, purpose, condition and concession, are expressed predominantly by means of adverbial clauses. Modal adverbials express the speaker's stance towards the statement that is being made. The range of adverbial relationships that can be expressed by postpositional phrases and adverbial clauses is extremely wide.