The label noun refers to the part of speech which includes the words dog, tree, house, number and honesty. The easiest way to identify nouns is to consider the following frames: The ————– was sweet; The —————— were sweet. Any single word which can fill one of the blanks to produce a grammatical sentence is a noun, because the English grammar permits nouns, and only nouns, to fill such positions. So for example, girl(s), boy(s), apple(s), mango(es) and several other similar words can fit into one of the blanks, and hence these words can be nouns in English.

English nouns distinguish number: that is, most nouns can be either singular or plural.

Noun clause

The label noun clause refers to any kind of subordinate clause which can occupy the position of a noun or noun phrase. It can, for example, be the subject of a verb. It can also be the object of a verb.

She has decided that she will find a good job. (Here the noun clause ‘that she will find a good job’ is the object of the verb decided.)
That she has not yet arrived worries me. (Here the noun clause ‘that she has not yet arrived’ is the subject of the verb worries.)

Noun phrase

A noun phrase is a syntactic unit which can serve as subject, direct object or object of a preposition in a sentence. A noun phrase is constructed around a noun or a pronoun as its head. A noun phrase may be of any size.  The simplest form consists of just one word.