antibody

This term carries a strong connotation of defense and specificity. It evokes the image of a biological lock-and-key mechanism where a precise molecule is crafted to recognize and bind to a specific foreign invader, effectively marking it for destruction. In medical and scientific discourse, it is used with a high degree of precision to distinguish between active immunity and passive immunity. While a layman might use it to mean general immunity, a professional uses it to refer to the actual physical protein circulating in the blood.