An expression referring to another expression. In stricter uses, an expression referring to something earlier in the discourse or, even more strictly, only reflexive and reciprocal pronouns.
An expression that features tautology.
Redundant use of words, a pleonasm, an unnecessary and tedious repetition.
A statement that is true for all truth values of its Boolean atoms.
A statement that is true for all truth values of its propositional variables.