in vivo

/ɪn ˌviˈvoʊ/

In vivo is a scientific term indicating that something has been observed in a living being, as in an animal experiment or a clinical trial of a new drug.

If you were testing your new energy drink by observing a group of subjects as they tried it, you could say your experiment was in vivo, or tested on living people. In vivo is easy to confuse with in vitro, which sounds similar but is actually its exact opposite, testing in an artificially controlled environment. The Latin translation of in vivo is "in a living thing."

Definitions of in vivo

1. adverb

   in the living organism
   “studies conducted in vivo”
2. adjective

   within a living organism
   “in vivo techniques”

   antonyms:

   in vitro

   in an artificial environment outside the living organism