n. pl. phi·los·o·phies
1. The study of the nature, causes, or principles of reality, knowledge, or values, based on logical reasoning.
2. A system of thought based on or involving such study: the philosophy of Hume.
3. The study of the theoretical underpinnings of a particular field or discipline: the philosophy of history.
4. An underlying theory or set of ideas relating to a particular field of activity or to life as a whole: an original philosophy of advertising; an unusual philosophy of life.
[Middle English philosophie, from Old French, from Latin philosophia, from Greek philosophiā, from philosophos, lover of wisdom, philosopher; see PHILOSOPHER.]
The American Heritage® Dictionary of the English Language, Fifth Edition copyright ©2020 by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
Indo-European & Semitic Roots Appendices
Thousands of entries in the dictionary include etymologies that trace their origins back to reconstructed proto-languages. You can obtain more information about these forms in our online appendices:
The Indo-European appendix covers nearly half of the Indo-European roots that have left their mark on English words. A more complete treatment of Indo-European roots and the English words derived from them is available in our Dictionary of Indo-European Roots.