Parts of Sentences: Subject, Predicate, Object, Indirect Object, Complement
Every word in a sentence serves a specific purpose within the structure of that particular sentence. According to rules of grammar, sentence structure can sometimes be quite complicated. For the sake of simplicity, however, the basic parts of a sentence are discussed here.
The two most basic parts of a sentence are the subject and predicate.
SUBJECT
The subject of a sentence is the person, place, or thing that is performing the action of the sentence. The subject represents what or whom the sentence is about. The simple subject usually contains a noun or pronoun and can include modifying words, phrases, or clauses.
The man . . .
PREDICATE
The predicate expresses action or being within the sentence. The simple predicate contains the verb and can also contain modifying words, phrases, or clauses.
The man / builds a house.
The subject and predicate make up the two basic structural parts of any complete sentence. In addition, there are other elements, contained within the subject or predicate, that add meaning or detail. These elements include the direct object, indirect object, and subject complement. All of these elements can be expanded and further combined into simple, compound, complex, or compound/complex sentences. (See TIP Sheet on "Sentence Type and Purpose.")
DIRECT OBJECT
The direct object receives the action of the sentence. The direct object is usually a noun or pronoun.
The man builds a house.
The man builds it.
INDIRECT OBJECT
The indirect object indicates to whom or for whom the action of the sentence is being done. The indirect object is usually a noun or pronoun.
The man builds his family a house.
The man builds them a house.
SUBJECT COMPLEMENT
A subject complement either renames or describes the subject, and therefore is usually a noun, pronoun, or adjective. Subject complements occur when there is a linking verb within the sentence (often a linking verb is a form of the verb to be).
The man is a good father. (father = noun which renames the subject)
The man seems kind. (kind = adjective which describes the subject)
Note: As an example of the difference between parts of speech and parts of a sentence, a noun can function within a sentence as subject, direct object, indirect object, object of a preposition, or subject complement.
For more information on the structure and formation of sentences, see the following TIP Sheets:
Sentence Types and Purposes
Sentence Fragments
Independent and Dependent Clauses: Coordination and Subordination
Prepositions and Prepositional Phrases
Other Phrases: Verbal, Appositive, Absolute
Comma Splices and Run-on Sentences
The Eight Parts of Speech
Nouns
Pronouns
Verbs
Adjectives
Adverbes
Conjunctions
Interjections
A sentence is a group of words that contains three things:
- A subject (that makes sense with the verb
- A verb (that goes with the subject)
- A complete thought
A sentence fragment is a group of words that lacks one or more of these three things. While there are many ways to end up with a fragment, almost every fragment is simply a result of one of the following three problems:
- It is missing a subject
- It is missing a verb.
- It fails to complete the thought it starts.
Fragments are no big deal in conversation; spoken English is full of them. In fact, if you spoke in complete sentences for one entire day, you would probably get some strange looks. But English conventions require that you avoid writing fragments (except in very rare instances), so you must be able to identify them in your writing and fix them.
To begin to identify fragments in your writing, read a sentence aloud. Does it sound complete? If you walked up to a stranger and said it to him, would it sound like a complete thought to him? Or would he be waiting expectantly for you to finish? Even if it sounds okay to you (because you already know what you mean), look at it and identify the subject (who or what did the action) and the verb (what the subject did) to make sure they're there. (For help identifying subjects and verbs, see the TIP Sheet Parts of Sentences.) If you think a subject is missing, or the verb sounds a little strange, or the thought is left hanging, refer to the tips below.
Missing subjects
Some fragments are missing subjects. Often the subject appears nearby, perhaps in the preceding sentence; however, each sentence must have a subject of its own. The following fragment lacks a subject:
Fragment
Was running late that day.
Who was running late? The instructor? The train? The simplest (but by no means only) way to correct this fragment is to add a subject:
I was running late that day.
Phrases which include words ending in -ing often appear as fragments:
Fragment
Biking and swimming after work on Thursday.
What about biking and swimming? Who is biking and swimming? Are you proposing that we all go biking and swimming? Add both a subject and a verb to correct this (again, not the only solution):
Mitchell went biking and swimming after work on Thursday.
Another suspect in the missing subject category is a phrase like this one:
Fragment
To register for class before the deadline.
Who wants to register? Or failed to register? Or plans to register? This fragment lacks both subject and verb. ("To register" is not really a verb, but another thing entirely; see the TIP Sheet Other Phrases: Verbal, Appositive, Absolute). The simplest fix is to add a subject and verb:
Stan hopes to register for class before the deadline.
(Avoid the mistake of thinking that a command, demand, or request lacks a subject. This kind of sentence has an unstated subject, you. So the subject of "Turn in your schedule changes at the counter" is you: "[You] turn in your schedule changes at the counter.")
Missing verbs
Some fragments are fragments because they are missing a verb or an essential part of a verb. Any phrase, no matter how long, is a fragment if the verb is missing:
Fragment
The birch trees with their rattling yellow leaves.
What about the birch trees? Adding a verb makes this fragment complete:
The birch trees with their rattling yellow leaves swayed in the wind.
Some verbs require helpers in order to be complete. Words ending in -ing, for example, must include helpers such as is, are, was, were, will be, or has been to be real verbs; without these helpers, they are not verbs. (If you want to know more about verb look-alikes, see the TIP Sheet Other Phrases: Verbal, Appositive, Absolute.) The fragment below contains an incomplete verb:
Fragment
Caroline studying her sociology tonight at Moxie's downtown.
Did your ear hear the strangeness? Add helpers to make the verb complete and repair the fragment:
Caroline will be studying her sociology tonight at Moxie's downtown.
Unfinished thoughts
A very common type of fragment is the unfinished thought fragment. While other kinds of fragments require you to add something--a subject, or a verb, or both--you can often fix unfinished thought fragments simply by joining them to a preceding or following sentence. The following example, while it contains a subject and a verb, fails to complete the thought:
Fragment
Because tuition increased again this semester.
The word to blame for making this thought incomplete is because. (Contrary to rumor, it's perfectly okay to start a sentence with because; you just have to finish what you're saying--in the same sentence.) If you find a fragment of this kind, see if the sentence before or the sentence after it would complete it:
Because tuition increased again this semester, Kou got a second job as a Student Assistant.
Or
Kou must take fewer units because tuition increased again this semester.
If the preceding or following sentence does not complete the unfinished thought, add the missing information to the fragment to make it complete. There are many words that, by their mere presence, make a clause incomplete, for example, since, while, when, unless, although. For more about these words, see the TIP Sheet Independent & Dependent Clauses.
In spite of the rules of grammar, language is plastic and can be shaped a great many ways, so for any fragment problem, many solutions exist. The more you practice writing, the more you will be able to spot fragments and fix them. And the more you learn about English, the more ways you will find to make your grammatically correct sentences say exactly what you mean.
RUN-ON SENTENCES AND COMMA SPLICES
Run-on sentences can be divided into two types. The first occurs when a writer puts no mark of punctuation and no coordinating conjunction between independent clauses. The second is called a comma splice, which occurs when two or more independent clauses are joined by just a comma and no coordinating conjunction.
Example of a run-on sentence:
The flowers are beautiful they brighten the room. (Incorrect)
Example of a comma splice:
The flowers are beautiful, they brighten the room. (Incorrect)
Examples of correct alternatives:
The flowers are beautiful. They brighten the room.
The flowers are beautiful; they brighten the room.
The flowers are beautiful, and they brighten the room.
The flowers are beautiful because they brighten the room.
A run-on sentence is not defined by its length! The fact that a sentence is very long does not automatically make it a run-on sentence. As you will see, the sentence structure and use of punctuation determine whether a sentence is a run-on.
In order to better understand run-on sentences and comma splices, it is important to review the basics of writing a grammatically correct simple sentence:
| A simple sentence is made up of only one independent clause. An independent clause is a group of words that contains a subject and a predicate and forms a complete thought when standing alone. The subject refers to someone or something (the subject contains at least one noun or pronoun). The predicate refers to what the subject does or is (the predicate contains the verb or verbs). Both the subject and predicate can contain additional descriptive elements, such as adverbs, adjectives, prepositions, or other modifying phrases, but in its most basic form the subject is the part of the sentence that contains the noun, and the predicate contains the verb. |
A sentence can be complete and correct with one basic independent clause made up of one subject plus its corresponding predicate. To demonstrate the basic structure of a simple sentence, find the noun that forms the subject and divide it from the verb.
| Subject | Predicate | Sentence |
| I | am. | I am. |
| The man | studied. | The man studied. |
| A frog | jumped. | A frog jumped. |
| Lola | sings. | Lola sings. |
By dividing the noun and verb, we can add modifiers to a simple sentence and still see the two basic parts, the subject and the predicate.
| Subject | Predicate |
| The man | studied. |
| The kind man | studied hard. |
| The kind man at the library | studied hard for the test on Friday. |
When looking at the structure of an independent clause, it is helpful to think of all elements of the subject separately from all elements of the predicate. Together the subject and predicate form the two basic and separate parts of each clause.
| Subject | Predicate |
| The kind man and his wife | studied hard for the test and read a book. |
| The man, his wife, and their child | studied hard, read books, and ate dinner. |
If the independent clause forms a complete thought, a period at the end demonstrates that the sentence is complete. The period means STOP. The sentence has ended, and a new sentence will begin.
Run-ons and comma splices occur when more than one subject/predicate pair exists in the sentence. When one subject/predicate pair is followed by an additional subject/predicate pair within one sentence (forming separate independent clauses), they need to be separated (or joined) according to very specific rules of punctuation and grammar.
Look at the following example of a run-on sentence:
The kind man studied hard his wife read a book. (Incorrect)
If we divide the sentence into subject/predicate pairs (each an independent clause), we see that two independent clauses exist, one following the other:
| First independent clause | Second independent clause | ||
| Subject | Predicate | Subject | Predicate |
| The kind man | studied hard | his wife | read a book. |
Without the correct separation, the two independent clauses written together form a run-on sentence. Once you can identify a run-on sentence by its incorrect structure, it is not hard to find a way to correct it.
When two independent clauses appear in one sentence, they must be joined (or separated) in one of four ways:
1. The two clauses can be made into two separate sentences by adding a period.
2. The two clauses can be joined by a comma and a coordinating conjunction (comma plus: and, but, or, nor, for, so, yet).
3. The two clauses can be joined by a semicolon.
4. The two clauses can be rewritten by adding, changing, rearranging, or deleting words. The simplest way to accomplish this is to add a subordinating conjunction between the clauses.
Notice that joining the independent clauses by a comma alone is NOT a choice. When two independent clauses are joined by only a comma, this error is called a comma splice.
The table below demonstrates the four correct options. When two independent clauses appear in a sentence, try to imagine a middle column in which only four possibilities exist to join the two clauses:
| First independent clause | Second independent clause | |||
| Subject | Predicate | 4 CORRECT OPTIONS | Subject | Predicate |
| The kind man | studied hard | . (period) | His wife | read a book. |
| The kind man | studied hard | , and , but , or , for , nor , so , yet (comma plus a coordinating conjunction) | his wife | read a book. |
| The kind man | studied hard | ; (semicolon) | his wife | read a book. |
| The kind man | studied hard | while after as because . . . (examples of subordinating conjunctions - no comma required) | his wife | read a book. |
Please note again that in the above examples a comma alone is NOT one of the correct options.
The kind man studied hard, his wife read a book. (Incorrect)
A comma alone between two independent clauses creates an incorrect comma splice.
Summary (Including Related Grammar Rules)
1. An independent clause contains one subject/predicate pair and expresses a complete thought.
Music makes my life worth living.
| Subject | Predicate |
| Music | makes my life worth living. |
2. A simple sentence is made up of only one independent clause:
Music makes my life worth living.
3. A run-on sentence is made up of two or more independent clauses that are not joined correctly or which should be made into separate sentences. A run-on sentence is defined by its grammatical structure, not its length.
Incorrect: My favorite band is in town they are performing now.
Correct: My favorite band is in town. They are performing now.
Correct: My favorite band is in town, and they are performing now.
4. A comma splice is the incorrect use of a comma to join two independent clauses.
Incorrect: I love classical music, it makes me feel joyful.
Correct: I love classical music because it makes me feel joyful.
Correct: I love classical music; it makes me feel joyful.
5. A compound sentence contains two or more independent clauses that are correctly joined by a comma plus a coordinating conjunction or by a semicolon:
Music means a lot to me, and certain songs bring wonderful memories to mind.
| First independent clause | Second independent clause | |||
| Subject | Predicate | Comma and coordinating conjunction | Subject | Predicate |
| Music | means a lot to me | , and | certain songs | bring wonderful memories to mind. |
Music means a lot to me; certain songs bring wonderful memories to mind.
| First independent clause | Second independent clause | |||
| Subject | Predicate | Semicolon | Subject | Predicate |
| Music | means a lot to me | ; | certain songs | bring wonderful memories to mind. |
6. A comma plus a coordinating conjunction can connect independent clauses correctly. There are seven coordinating conjunctions (sometimes remembered by the acronym "fanboys"):
for, and, nor, but, or, yet, so
7. A complex sentence contains one independent clause and one or more dependent clauses. The dependent clause begins with a subordinating conjunction:
I always think of summer whenever they play that song.
| First independent clause | Second independent clause | |||
| Subject | Predicate | Subordinating conjunction | Subject | Predicate |
| I | always think of summer | whenever | they | play that song. |
8. A subordinating conjunction connects a dependent clause to an independent clause. The dependent clause cannot stand alone; it requires attachment to an independent clause in order to express the complete meaning of the sentence. The following are examples of some of the most common subordinating conjunctions:
after, although, as, as if, because, before, even though, if, in order that, rather than, since, so that, than, that, though, unless, until, when, whenever, where, wherever, whether, while
For more information, please see the following TIP Sheets:
Independent and Dependent Clauses: Coordination and Subordination
Sentence Type and Purpose
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