In grammar, a part of speech (also a word class, a lexical class, or a lexical category) is a linguistic category of words (or more precisely lexical items), which is generally defined by the syntactic or morphological behaviour of the lexical item in question. Common linguistic categories include noun and verb, among others. There are open word classes, which constantly acquire new members, and closed word classes, which acquire new members infrequently if at all.
Almost all languages have the lexical categories noun and verb, but beyond these there are significant variations in different languages. For example, Japanese has as many as three classes of adjectives where English has one; Chinese, Korean and Japanese have nominal classifiers whereas European languages do not; many languages do not have a distinction between adjectives and adverbs, adjectives and verbs (see stative verbs) or adjectives and nouns]citation needed[, etc. This variation in the number of categories and their identifying properties entails that analysis be done for each individual language. Nevertheless the labels for each category are assigned on the basis of universal criteria.
A syntactic category is a type of syntactic unit that theories of syntax assume. The traditional parts of speech (e.g. noun, verb, preposition, etc.) are syntactic categories, and in phrase structure grammars, the phrasal categories (e.g. noun phrase NP, verb phrase VP, prepositional phrase PP, etc.) are also syntactic categories. Phrase structure grammars draw an important distinction between lexical categories and phrasal categories. Dependency grammars, in contrast, do not acknowledge phrasal categories (at least not in the traditional sense), which means they work with lexical categories alone. Many grammars also draw a distinction between lexical categories and functional categories. In this regard, the terminology is by no means consistent. The one opposition (lexical category vs. phrasal category) and the other opposition (lexical category vs. functional category) are orthogonal to each other. The category types just mentioned (lexical, phrasal, functional) should not be confused with grammatical categories (also known as grammatical features), which are properties such as tense, gender, etc.
At least three criteria are used in defining syntactic categories:
An adverb clause is a dependent clause that functions as an adverb. In other words, it contains a subject (explicit or implied) and a predicate, and it modifies a verb.
According to Sidney Greenbaum and Randolph Quirk, adverbial clauses function mainly as adjuncts or disjuncts. In these functions they are like adverbial phrases, but due to their potentiality for greater explicitness, they are more often like prepositional phrases (Greenbaum and Quirk,1990):
In Latin and English grammar, the gerund is a non-finite verb form that can function as a noun. The English gerund ends in -ing (as in I enjoy playing basketball); the same verb form also serves as the English present participle (which has an adjectival or adverbial function), and as a pure verbal noun. The gerund is the form that names the action of the verb (for instance, playing is the action of "to play"). In some cases a noun ending in -ing sometimes serves as a gerund (as in I like building things, I like painting / I like painting pictures, and I like writing / I like writing novels), while at other times serving as a non-gerund indicating the product resulting from an action (as in I work in that building, That is a good painting, and Her writing is good). The latter case can often be distinguished by the presence of a determiner before the noun, such as that, a, or her in these examples.
The Latin gerund (gerundium) is a verb form which behaves similarly to a noun, although it can only appear in certain oblique cases. (It should not be confused with the Latin gerundive, which is similar in form, but has a passive, adjectival use.)