Nonlinear

Nonlinear means when one change affects another change in an uneven way. For example, if you add two blocks to a tower it doesn't just get two times as tall. It can depend on how the blocks are arranged, so the tower can get taller or shorter than double the height. Nonlinear means that it's hard to predict how the tower will change when you add a block because the changes will depend on how the blocks are arranged.