Complete Sentences

A complete sentence is also known as an independent clause; it is a sentence that forms a complete thought. To be complete, all a sentence needs is a subject (a noun or pronoun) and a main verb that the noun performs. For example, "Jack runs" is a complete sentence. But, of course, sentences can get much more complex (and you'll be sure to see that on the SAT), by adding modifiers, adjectives, and other elements.

An incomplete sentence, is a clause that does not form a complete thought. Types of incomplete sentences include sentence fragments and dependent clauses. There are a few different things that can disqualify a clause or phrase from being a complete sentence. This could be because it's lacking a subject, like "Running a marathon", or because it's lacking a main verb, like "The concert in the city". But it's also important to note not every form of a verb can count as a main verb. "-ing" verbs can't serve as a main verb on their own ("Jack running" is an incomplete sentence because "running" is not a main verb). However, "-ing" verbs can come after another verb to form a main verb phrase ("Jack is running"). Similarly, "to" verbs can't serve as a main verb on their own ("Jack to run" doesn't work), but can come after another verb to form a main verb phrase ("Jack likes to run"). Another thing that can disqualify a sentence from being a complete sentence is when you add a certain type of word to the start of the sentence. For example, "Although Jack runs" is not a complete sentence even though it seems to have a subject and a main verb. These types of words are called subordinating conjunctions, and include words like "although", "since", "as", "because", and "while". These words begin dependent clauses, which might come before, after, or in the middle of a complete sentence.

You can't just stick two complete sentences together to form a longer sentence. For example, "Jack runs Kelly swims" is not a proper sentence. While this probably seems obvious, when sentences get more complex in can sometimes be more difficult to spot when two complete sentences are combined inapproproriately. So what are the actual rules for combining and separating complete sentences? There are several forms of punctuation that can be used to separate or combine complete sentences:

• Period
  This is the most obvious way to separate two complete sentences. For example, "Jack runs. Kelly swims."
• Semicolons
  A semicolon can also be used to separate two complete sentences. For example, "Jack runs; he's hoping to qualify for the Boston Marathon."
• Comma + FANBOYS
  A comma + a FANBOYS conjuction (for, and, nor, but, or, yet, so) can also come in between two complete sentences. For example, "Jack runs, and he's hoping to qualify for the Boston Marathon."