Part of Speech is the grammatical function of a word/group of words.

Part of Speech is the grammatical function of a word/group of words.
Some English words may have only one function (for example, and as a conjunction).
Others may have several functions (for example, fancy, which is a noun in the phrase
„flights of fancy‟, a verb in „Fancy that!‟ and an adjective in „a fancy hat‟).
Other examples:
A characteristic feature (noun)
To feature in a film, etc. (verb)
A feature film (adjective)
Ann came in early (adverb)
She is an early bird! (adjective)
In the so-called „developing‟ countries the divide between the rich and the poor is ever
increasing. (nouns)
The poor people get poorer, whereas the rich elite gets richer. (adjectives)
Figure of speech (noun)
It is difficult to figure out his meaning. (verb)
Figure skating (adjective)
These are examples of single words fulfilling different functions. However, whole groups
of words often work together as one unit, fulfilling one function. They then form phrases
or clauses. What are they? We already know that both are groups of words. But before
considering the difference between them, we need to understand the concept of clause
and consider the basic sentence structure.

Concept # 2: Clauses and their Basic Structure Pattern (S/FiniteV/C). Clauses are
groups of words that have a Subject (what we speak about) and a Finite Verb (what we
say about the Subject). The Finite Verb conforms to its Subject in number and person:
this Subject-Verb Agreement is essential to sentence grammaticality. Both Subject and
its Verb may have modifiers.
Basic Sentence Pattern: (S/V/C). Most declarative English sentences follow the S/V/C
pattern: the Subject + its modifiers (what we speak about) fill the first slot / the Finite
Verb and its modifiers fill the second slot / and Compliment (optional) takes the third slot
(S/V/C). Compliment may be made up of:
o Zero Compliment
o Predicate Adjective (PA)
o Predicate Noun (PN)
o Direct/Indirect Object (DO/IO)
Together /V/C make up the Predicate, or what we say about the Subject. The „heart‟ of the predicate is the
finite verb, which may be separated from its Subject by modifiers (other words, phrases, or even clauses). It
is important that the Subject-Verb Agreement is maintained despite the intervening words: without the
Subject-Verb Agreement the sentence becomes ungrammatical (as in „Mary am a clever girl‟).
Examples:
S / V / C (PN)
Ignorance / is / the mother of devotion. (Robert Burton)
S / V / C (PA+or+PA)
Nothing / is / good or bad/.
Conj / S2 / V2 / C (DO)
But / thinking / makes / it.
(Shakespeare)