Punctuation marks (such as commas, apostrophes, and colons) help to improve the clarity of your work and keep your argument focused. Check out our topical guides to different punctuation marks by clicking the links at the left. You can also test your knowledge of punctuation with our self-guided quizzes. Finally, Grammarly, an automated grammar tutor available for free to Walden students, can help you identify punctuation and other errors in your writing.