Abnormal or unusual: a state or condition that deviates from the normal, often referring to illness, malfunction, or anomaly (antonym: 正常).
体温に異常があるので病院へ行ったほうがいい。
You should see a doctor because your temperature is abnormal.
システムで異常が検出されたため、サービスを停止した。
An anomaly was detected in the system, so the service was stopped.
今日は異常に寒く、外出には注意が必要だ。
It's unusually cold today, so caution is needed when going out.