A protective substance that exists in the serum or other bodily fluid and is capable of killing microorganisms; complement.

Something (or someone) that completes; the consummation.

The act of completing something, or the fact of being complete; completion, completeness, fulfilment.

The totality, the full amount or number which completes something.

To complete, to bring to perfection, to make whole.

“We believe your addition will complement the team.”

To provide what the partner lacks and lack what the partner provides, thus forming part of a whole.

“I believe our talents really complement each other.”

To change a voltage, number, color, etc. to its complement.

A good whose appeal increases with the popularity of its complement