Complementarity

Complementarity - a relation between two opposite states or principles that together exhaust the possibilities. In other words, when two things complement each other they make a whole (1) or cancel each other out completely (0) - Yin and Yang, male and female, positive and negative etc.

This is (for my way of thinking as a physicist) best thought of in terms of logic gates.

Here we have and as inputs into an AND gate. Both inputs have to high for the output to be high... and as one of them HAS to be low (as it is the opposite of the other) the output will always be zero!

		Output
0	1	0
1	0	0

Here we have and as inputs into an OR gate. If either input is high the gate output will be high... and as one of them HAS to be high the output will always be high

		Output
0	1	1
1	0	1