It is seldom possible to ask a research question in only one way, using a single vocabulary, and expect to find all the material you will need to complete a research project.
Many databases have their own vocabulary, their own way of referring to the topics they cover.
Often this vocabulary is that of the profession or discipline which created the database. As you move from one database to another, try to be aware of any changes in the way a particular database is referring to your topic, and be prepared to change vocabulary, if necessary. You may need to find information in different kinds of sources . Books tend to be longer, and broader in scope, than magazine or journal articles. Therefore, the search vocabulary required for finding them may be somewhat broader in scope than that for articles.