I hear that when you come together as a church, there are divisions among you, and to some extent I believe it. No doubt there have to be differences among you to show which of you have God’s approval.

(1 Corinthians 11:18-19)

The word that is translated ‘differences’ is αἵρεσις hairesis or heresy.

The English language borrowed words from other languages (notably Greek) for concepts our pagan forebears did not have before becoming Christian.  For example, standing in alignment (rihtwis, the right-wise or way) with your king was critical, so we have righteous; but how and why you chose your deity was not: Frige, Thor, Wotan, Tiw, take your pick; mix and match!