What is the definition of when each input has exactly one output in a relation

The word you’re looking for is a *function*. Functions can’t have one input associated with more than one output, but multiple inputs *can* produce the same output (so-called “even functions” have this property), and the special functions where each output has exactly one input associated with it are called “one-to-one” functions.

They sought new allies to germany tried to get mexico to join and put pressure on the us. the us joined the allies because of the lucitania

Answer is a not really sure tho