e·pis·te·mol·o·gy (ĭ-pĭs'tə-mŏl'ə-jē) n. The branch of philosophy that studies the nature of knowledge, its presuppositions and foundations, and its extent and validity.
[Greek epistēmē, knowledge (from epistasthai, epistē-, to understand : epi-, epi- + histasthai, middle voice of histanai, to place, determine; see stā- in Indo-European roots) + -logy.] e·pis'te·mo·log'i·cal (-mə-lŏj'ĭ-kəl) adj., e·pis'te·mo·log'i·cal·ly adv., e·pis'te·mol'o·gist n.