Something that is bad is unpleasant, harmful, or undesirable.

You use bad to indicate that something unpleasant or undesirable is severe or great in degree.

A bad idea, decision, or method is not sensible or not correct.

If you describe a piece of news, an action, or a sign as bad, you mean that it is unlikely to result in benefit or success.

Something that is bad is of an unacceptably low standard, quality, or amount.

Someone who is bad at doing something is not skilful or successful at it.

If you say that it is bad that something happens, you mean it is unacceptable, unfortunate, or wrong.

You can say that something is not bad to mean that it is quite good or acceptable, especially when you are rather surprised about this.

A bad person has morally unacceptable attitudes and behaviour.

A bad child disobeys rules and instructions or does not behave in a polite and correct way.

If you are in a bad mood, you are angry and behave unpleasantly to people.

If you feel bad about something, you feel rather sorry or guilty about it.

If you have a bad back, heart, leg, or eye, it is injured, diseased, or weak.

Food that has gone bad is not suitable to eat because it has started to decay.

Bad language is language that contains offensive words such as swear words.

If you say that it is too bad that something is the case, you mean you are sorry or sad that it is the case.

If you say 'too bad', you are indicating that nothing can be done to change the situation, and that you do not feel sorry or sympathetic about this.

If someone or something is in a bad way, they are in a bad condition or situation.

If nobody has a bad word to say about you, you are liked or admired by everyone.