If you say that something is irrelevant, you mean that it is not important in a situation. The choice of subject matter is irrelevant. not useful or not relating to a particular situation, and therefore not important relevant
If you describe something such as a fact or remark as irrelevant, you mean that it is not connected with what you are discussing or dealing with. The government decided that their testimony would be irrelevant to the case. relevant + irrelevantly ir·rel·evant·ly She would have hated the suit, I thought irrelevantly