Q: Should all my keywords be words or phrases mentioned in my paper or can I also use synonyms?
Hello Djili – Welcome to the forum! Straight away, you have asked a pertinent question. To answer your question equally straight away, no, it’s not necessary to have keywords that are only words or phrases used in your paper, and yes, they can also be synonyms. In fact, you should have variant words and phrases as keywords because potential readers can search for papers around your topic using different but related terms from what you have used in your paper. So, to increase the chances of your paper being discovered (and therefore, read), you should go ahead and include some more.
For more information on the topic, here’s a related query you may go through: How to create keywords for a research paper
And here’s a bigger piece on crafting the right title and abstract (along with keywords) for your paper: How to write an effective title and abstract and choose appropriate keywords
Finally, if you are close to submission, you may wish to consider any of our editing services to help review and edit your paper, thereby increasing its chances of acceptance. Learn more here: Editage Editing Services
Hope that helps. And all the best for your paper!