However, you must be careful where you truncate the term. If you truncated plagiarism by using plag*, you will retrieve items that include terms such as plague and plagues, in addition to plagiarism.
Conversely, if you truncated the term using plagiaris*, you would exclude the terms plagiarize, plagiarizing, etc.
As much as possible, you should use truncation symbols so that you include only the variants of your search term. The search tips or help button in a database will often tell you which truncation symbol to use in that system.