Single terms, phrases, and so on can be combined using "NOT" in upper, lower, or mixed case, or prefixed with "!" or "-".
These queries search for nodes that contain the terms yellow in any content.
yellow NOT banana yellow !banana yellow -banana NOT yellow banana -yellow banana !yellow banana
The NOT operator can only be used for string keywords; it doesn't work for numerals or dates.
Prefixing any search qualifier with a - excludes all results that are matched by that qualifier.