Easton's Bible Dictionary: M. G. Easton, M.A., D.D.
From a Greek word signifying
In the Acts of the Apostles (Acts 5:17, 15:5, 24:5, 14, 26:5) it denotes a sect, without reference to its character. Elsewhere, however, in the New Testament it has a different meaning attached to it. Paul ranks "heresies" with crimes and seditions (Gal. 5:20). This word also denotes divisions or schisms in the church (1 Cor. 11:19). In Tit. 3:10 a "heretical person" is one who follows his own self-willed "questions," and who is to be avoided. Heresies thus came to signify self-chosen doctrines not emanating from God (2 Pet. 2:1).