1. the rational investigation of the truths and principles of being, knowledge, or conduct.
2. any of the three branches, namely natural philosophy, moral philosophy, and metaphysical philosophy, that are accepted as composing this study.
4. the critical study of the basic principles and concepts of a particular branch of knowledge, especially with a view to improving or reconstituting them: the philosophy of science.
5. a system of principles for guidance in practical affairs.
6. a philosophical attitude, as one of composure and calm in the presence of troubles or annoyances.