With the RegEx “solution”, it can be nice to use \b which just means at the beginning or end of the word.
\bred\b means that red has to be at the start and the end, i.e. the isolated word “red”
\bred means that red only has to be at the start of a word.
red\b means that red only has to be at the end of a word.
\bred\b will find “the red dog” but not the “the redwood tree” and not “covered up”
red\b will find “the red dog” and “covered up” but not “the redwood tree”
\bred will find “the red dog” and “the redwood tree” but not “covered up”
/\bred/ will find any entry with a word starting with the letters: red
This seems a little less complicated than other suggestions that have been made.