Are contractions (e.g., I'm or isn't) acceptable in academic writing?
Contractions, in which two words are shortened and combined into one word (e.g., "I'm" and "isn't"), are usually reserved for informal communication. Since academic writing typically has a formal style, contractions should generally be avoided. Instead, spell out the words in full: "I am" and "is not". If you are writing a document that requires an informal style, you could check with your instructor as to whether contractions are acceptable.
For more information and suggestions of when contractions may be appropriate in scholarly writing, please visit "Contractions in Formal Writing: What's Allowed, What's Not" from the APA Style Blog.