To act or behave in a specified manner toward. To regard and handle in a certain way. Often used with as: treated the matter as a joke. To deal with in writing or speech; discuss: a book that treats all aspects of health care. To deal with or represent artistically in a specified manner or style: treats the subject poetically. To provide with food, entertainment, or gifts at one's own expense: treated her sister to the theater. To give (someone or oneself) something pleasurable: treated herself to a day in the country. To subject to a process, action, or change, especially to a chemical or physical process or application. To give medical aid to (someone): treated many patients in the emergency room. To give medical aid to counteract (a disease or condition): treated malaria with quinine. To deal with a subject or topic in writing or speech. Often used with of: The essay treats of courtly love. To pay for another's entertainment, food, or drink. To engage in negotiations, as to reach a settlement or agree on terms: "Both sides nonetheless are quite willing to treat with [the king]\u201d ( Gregory J. Wallance). Something, such as one's food or entertainment, that is paid for by someone else. A source of a special delight or pleasure: His trip abroad was a real treat.