What is a biconditional statement for the moon is the largest satellite of earth

Answer: The moon is the largest satellite if and only if it is for earth.

A combination of conditional and converse part of a statement is termed as biconditional statement. In mathematics, there is logic to put "if and only if" between the statement so the statement would be true from the both sides (conditional and converse) of the statement.

For example: Biconditional statement for statement ab is "a if and only if b" where a is hypothesis and b is result.