mentis

be compos mentis

To be sane or mentally competent. "Compos mentis" is Latin for "of sound mind." I doubt that Travis was compos mentis when he committed that crime.See also: compo, mentis

non compos (mentis)

Not sane or mentally competent. The phrase is Latin for "not of sound mind." Based on the orders he's been giving lately, many believe him to be non compos. The judge ruled that she had been non compos mentis at the time, and thus could not be held legally liable.See also: compo, non

be ˌcompos ˈmentis

(from Latin, formal or humorous) having full control of your mind: Are you sure she was fully compos mentis when she said that?See also: compo, mentis