Logical Symbols A ? B means if A is true then B is also true; if A is false then nothing is said about B. → may mean the same as ? (the symbol may also indicate the domain and codomain of a function; see table of mathematical symbols).

Logical Symbols

A ? B means if A is true then B is also true; if A is false then nothing is said about B.

→ may mean the same as ? (the symbol may also indicate the domain and codomain of a function; see table of mathematical symbols).

? may mean the same as ? (the symbol may also mean superset).

A ? B means A is true if B is true and A is false if B is false.

The statement ?A is true if and only if A is false.

The statement A ∧ B is true if A and B are both true; else it is false.

The statement A ∨ B is true if A or B (or both) are true; if both are false, the statement is false.

? x: P(x) means P(x) is true for all x.

? x: P(x) means there is at least one x such that P(x) is true.

?! x: P(x) means there is exactly one x such that P(x) is true.

x ? y means y is derived from x.