A phrase is a group of words functioning as a syntactical unit. It’s a broad term, comprising groups of words of many different types and functions. Phrases function as all parts of speech, as both subjects and predicates, as clauses, as idioms, and as figures of speech. This is by no means a complete list of the functions of phrases, though, as virtually any small group of words can be called a phrase.
There are no rules governing what does and what does not constitute a phrase. The term is not as specifically defined as, say, a clause. Think of a phrase as a group of words that go together somehow. For example, the dog on the roof is a phrase that functions as a noun, but the phrase can be broken down further into a noun phrase, the dog, and a prepositional phrase (which also functions as an adjectival phrase), on the roof.
Unlike a sentence or a clause, a phrase doesn’t need both a subject and a predicate. What can be said about phrases is that they usually have focal points, sometimes known as heads. For example, in the phrase the dog on the roof, the noun dog is the head because it determines the nature of the phrase. But not all phrases have heads. For example, the phrase big, red, and smelly is just a list of adjectives, so it does not have a head.
Types of phrases
In the simple sentence He ran, the verb ran can be modified in several ways. It can be modified with a single-word adverb—for example, He ran quickly, He ran wildly, or He ran backwards. Or the verb can be modified with a phrase—for example, He ran toward the ball, He ran for five miles, or He ran faster than a speeding bullet. In each of these examples, the phrase following ran qualifies the verb and is thus an adverbial phrase. Incidentally, the first two (toward the ball and for five miles) also qualify as prepositional phrases.
Here are some other examples of adverbial phrases:
Mrs Hilal speaks in a low, deep voice. [The phrase in a low, deep voice modifies speaks.]
Those concerns over possible double-dealing spiked a week ago … [Washington Post] [The phrase a week ago modifies spiked.]
The United States generally erred on the side of caution. [National Interest] [The phrase on the side of caution modifies erred.]
Adverbial phrases are commonly used to start sentences. These are usually set apart by commas—for example:
For decades, Utah let condemned prisoners choose whether to die by hanging or the firing squad … [New York Times] [For decades modifies let.]
In 1690, the Massachusetts Bay Colony became the first government in the Western world to issue paper money. [Wall Street Journal] [In 1690 modifies became.]
The main noun of a noun phrase is the head. It’s the one essential element of the phrase.
For example, this sentence has two noun phrases, overtures to Washington and recent days:
China has also made overtures to Washington in recent days. [NY Times]
The heads of these noun phrases are overtures and days.
And this sentence has two very long noun phrases:
He also warned that the problem of financial institutions being perceived as “too big to fail” has become prevalent, despite proposals in Congress that seek to permanently end taxpayer bailouts of large financial institutions. [NY Times]
The head of the of the noun phrase the problem of financial institutions being perceived as “too big to fail” is problem. The head of the noun phrase proposals in Congress that seek to permanently end taxpayer bailouts of large financial institutions is proposals. Both noun phrases contain smaller noun phrases—including financial institutions and taxpayer bailouts of large financial institutions.
A prepositional phrase is a phrase consisting of a preposition, its prepositional object, and any words modifying that object.
For him to do that took courage.
Prepositional phrases may also be adverbs (in which case they’re also known as adverbial phrases). In this sentence, for example, above the tree line modifies the verb walked:
We walked above the tree line.
And they may function as adjectives. In this sentence, for example, of the city modifies the noun streets:
We strolled the streets of the city.
Adjectival and adverbial phrases should be placed as near as possible to the words they modify. Otherwise, confusion can result. For example, this sentence is misleading:
I’m looking for a girl who was here an hour ago in a red dress.
This sentence would be clearer as,
I’m looking for a girl in a red dress who was here an hour ago.
Also, when a prepositional phrase modifies multiple elements in a list, the phrase should follow the last element—for example:
The bread, the apples, and the peanut butter in the kitchen all belong to Bill.