An appeal to authority is the use of the oral or written testimony of a recognized expert in the field. In many situations appealing to authorities is not only acceptable and sufficient but even a sometimes necessary argumentative technique.

Formally an appeal to authority lacks any substantive truth value of its own; asserting the truth based ONLY on the fact that a given socially-accepted authority figure also asserts this truth is a clear [[LogicalFallacy]].

(See AdVerecundiam, but note that appeal to "reverence" is slightly different!)