PowerPoint provides a default spelling dictionary which contains a list of all common words. But, when you are working on a particular project that uses uncommon words not found in everyday language, PowerPoint may mark some words as misspelled, even though they are correct. To solve this issue, you could edit a custom dictionary or load a ready-made 3rd party dictionary within PowerPoint 2011. Additionally, you can also create your own dictionary that includes a set of words for a particular project. So, if you need to do a legal presentation for a client once a year, you could create a separate dictionary for just this one project.