The three main search expressions, or operators, recognized by Boolean logic are:

• AND : Narrows the search by requiring that all the specified keywords must be present in the results. It combines terms so that only records containing all the terms are retrieved, thus reducing the number of results

• OR : Broadens the search by including results that contain any of the specified keywords. It retrieves records that have at least one of the terms, expanding the search to include synonyms or related concepts

• NOT : Narrows the search by excluding results that contain the term following NOT. It removes unwanted topics or concepts from the results, but should be used carefully as it can eliminate relevant items

These Boolean operators are fundamental in constructing logical search queries to refine and control search results in databases and search engines