The Greek verb apostygeō means to abhor, to detest utterly, to hate with horror. A strengthened form of stygeō (to hate/detest), the prefix apo- intensifies the aversion — a complete, visceral turning away from something regarded as vile.
Apostygeō appears only once in the NT: Romans 12:9, 'Hate what is evil' (apostygountes to ponēron). Paul's instruction is striking — the command uses the strongest Greek word for hatred/revulsion. This is not passive avoidance but active moral horror at evil. Christians are to have the same visceral aversion to sin that God has. The context is love: genuine love (agapē anypókritos — love without hypocrisy) is precisely what enables and requires this hatred. To truly love the good is to truly abhor its opposite. This is the counterpart to the positive commands that follow ('cling to what is good,' v.9b). The word resists a sentimental Christianity that calls evil 'just mistakes' — genuine moral love names evil as evil.