Search Engines only find words that appear on their algorithm-indexed webpages.
Unique words specific to your research
Multiple words with common synonyms
Example: The Keywords, human morality in Star Wars, would return results including the words morals, moral philosophy, ethics, movies, Star Wars...
Place quotation marks (" ") around multiple words
This searches for the phrase rather than the individual words
Search engines do not search for some words (i.e. an, and, the, I, where, what, how)
A (+) before a required word forces its inclusion in the results