Every sentence has a subject and a predicate. The subject of a sentence is the noun, pronoun, or phrase or clause the sentence is about, and the predicate is the rest of the sentence after the subject:

• Einstein’s general theory of relativity has been subjected to many tests of validity over the years.
• In a secure landfill, the soil on top and the cover block storm water intrusion into the landfill. (compound subject)
  • There are two subjects in this sentence: soil and cover.
  • Notice that the introductory phrase, “In a secure landfill,” is not a part of the subject or the predicate.
• The pressure is maintained at about 2250 pounds per square inch then lowered to form steam at about 600 pounds per square inch. (compound predicate)
  • There are two predicates in this sentence: “is maintained at about 2250 pounds per square inch” and “lowered to form steam at about 600 pounds per square inch”
• Surrounding the secure landfill on all sides are impermeable barrier walls. (inverted sentence pattern)
  • In an inverted sentence, the predicate comes before the subject. You won’t run into this sentence structure very often as it is pretty rare.

A predicate can include the verb, a direct object, and an indirect object.

Direct Object

A direct object—a noun, pronoun, phrase, or clause acting as a noun—takes the action of the main verb (e.g., the verb is happening to the object). A direct object can be identified by putting what?, which?, or whom? in its place.

• The housing assembly of a mechanical pencil contains the mechanical workings of the pencil.
• Lavoisier used curved glass discs fastened together at their rims, with wine filling the space between, to focus the sun’s rays to attain temperatures of 3000° F.
• The dust and smoke lofted into the air by nuclear explosions might cool the earth’s atmosphere some number of degrees.
• A 20 percent fluctuation in average global temperature could reduce biological activity, shift weather patterns, and ruin agriculture. (compound direct object)

Indirect Object

An indirect object—a noun, pronoun, phrase, or clause acting as a noun—receives the action expressed in the sentence. It can be identified by inserting to or for.

• The company is designing senior citizens a new walkway to the park area.
  • The company is not designing new models of senior citizens; they are designing a new walkway for senior citizens. Thus, senior citizens is the indirect object of this sentence.
• Please send the personnel office a resume so we can further review your candidacy.
  • You are not being asked to send the office somewhere; you’re being asked to send a resume to the office. Thus, the personnel office is the indirect object of this sentence.

Phrases and Clauses

Phrases and clauses are groups of words that act as a unit and perform a single function within a sentence. A phrase may have a partial subject or verb but not both; a dependent clause has both a subject and a verb (but is not a complete sentence). Here are a few examples (not all phrases are highlighted because some are embedded in others):

There are two types of clauses: dependent and independent. A dependent clauses is dependent on something else: it cannot stand on its own. An independent clause, on the other hand, is free to stand by itself.

So how can you tell if a clause is dependent or independent? Let’s take a look at two the clauses from the table above:

• when two oppositely charged bodies are brought close to one another
• Since the frequency is the speed of sound divided by the wavelength
• which, if current plans hold, will bring nuclear capacity to about 22% of all electrical capacity by 1995

These are all dependent clauses. Any clause with a subordinating conjunctions (like when or since) is a dependent clause. For example “I was a little girl in 1995” is an independent clause, but “Because I was a little girl in 1995” is a dependent clause. Clauses that start with relative pronouns, like which, also become dependent clauses.