Although you can receive a high score on the Analytical Writing Assessment even if your essays contain some grammatical errors, the official guidelines indicate that grammar is given some weight in the scoring. Knowing the rules that govern punctuation will reduce your error rate dramatically. Moreover, knowledge of grammar and punctuation will be invaluable in your graduate writing, where mistakes can be costly. In this section, we will discuss the most commonly used punctuation marks: commas, semicolons, colons, dashes, apostrophes, and quotation marks. We will also discuss the use of punctuation to correct run-on sentences and sentence fragments.