Ignoratio elenchi, also known as irrelevant conclusion, irrelevant thesis or fallacy of distraction, is the informal fallacy of presenting an argument that may in itself be valid, but does not address the issue in question. Arguments which shift the focus of debate to "safer" but less relevant ground fall into this category. The phrase ignoratio elenchi is from Latin, and can be roughly translated as "ignorance of refutation", that is, ignorance of what a refutation could logically be. Here elenchi is the genitive singular of the Latin noun elenchus, which is from the Greek ἔλεγχος elenchos, meaning an argument of disproof or refutation. This is one of the fallacies identified by Aristotle in his Organon. In a broader sense he asserted that all fallacies are a form of ignoratio elenchi.
An example might be a situation where A and B are discussing whether the law permits A to do something. If A attempts to support his position with an argument that shows that the law ought to allow him to do the thing in question, then he is guilty of ignoratio elenchi.
A related concept is that of the red herring, which is a deliberate attempt to divert a process of enquiry by changing the subject.
For example: "I think that we should make the academic requirements stricter for students. I recommend that you support this because we are in a budget crisis and we do not want our salaries affected."
Here the second sentence, though used to support the first, does not address the topic of the first sentence, instead switching the focus to the quite different topic of lecturer salaries.