Use the PowerPoint spell check and PowerPoint grammar check features to ensure your PowerPoint presentation is free of errors.
PowerPoint allows you to modify the proofing options, giving you more control over how it reviews your text. For example, you can customize the automatic spell check to change the way PowerPoint marks spelling errors. You can also enable the grammar check option to help you find and correct contextual spelling errors (like their vs. they're).
Modifying settings in PowerPoint Options—including proofing—will affect any presentation you edit in PowerPoint, not just your current presentation.