Which suffix means 'to kill'?

The suffix that means 'to kill' is indeed -cide. This suffix is derived from the Latin word "caedere," which means "to kill." It is commonly used in various contexts to indicate a substance or agent that kills something, such as in the terms "insecticide" (a substance that kills insects) and "pesticide" (a substance that kills pests). The use of this suffix is integral in medical terminology and various scientific fields, indicating an action of causing death to a specific target.

The other suffixes do not convey the same meaning. For example, -oid refers to resemblance or similarity, often appearing in words that indicate a likeness to something. -gravida is used in obstetrics to refer to pregnancy, specifically indicating the number of pregnancies a woman has had. -algia, on the other hand, refers to pain, as seen in terms like "neuralgia," which denotes nerve pain. Each suffix has a distinct meaning, but -cide specifically indicates an act of killing.