Plagiarism is to present your work with ideas or writings of another person without appropriate acknowledgement or referencing. It is still plagiarism even if you do it accidentally.
Ways for you to avoid plagiarism and its consequences are:
Paraphrasing is using your own words to restate someone’s ideas and must be correctly referenced in an assignment.
Visit the Academic Skills Essentials guide for more guidance on paraphrasing and other academic skills and writing advice.