The Latin noun probus, meaning “virtuous” or “worthy,” is the ultimate source of probe and probability and their variants, which are listed and defined in this post.
The verb probe is from the Latin word probare, derived from probus and meaning “demonstrate” or “test,” and means “examine” or “search.” The noun form, also probe, describes an investigation or search or a device for carrying out either type of procedure. A proband, meanwhile, is the first subject to be examined in a medical study to investigate, for example, a genetic disorder.
Probate refers, as a noun or a verb, to validation of a will, and probation is study of a person to determine his or her fitness for a position or for rehabilitation after committing a crime, or the period during which the study occurs. (Adjectival forms are probational and probationary, and the adverbial form is probationally.) The probationer, the person under probation, seeks to demonstrate probity; that word, directly derived from probus, means “virtue.” The adjective probative means “exploratory” or “substantiating” and, in legal contexts, “relating to proof” or “tending to prove.”
A reprobate is a person who demonstrates a lack of virtue. This term’s force has become diluted; it is now usually employed in a humorous sense as a synonym for rascal, but in the 1800s, it described a morally depraved person, and earlier, the connotation was of condemnation or damnation. As a verb, reprobate means “condemn,” “damn,” or “reject,” and it also serves as an adjective.
Probable and its permutations are also descended from probare. Probable and probably derive from the Latin word probabilis, meaning “acceptable” or “provable,” and are synonyms for the adjectival and adverbial forms of likely, while the quality of being probable—as well as the mathematical concept of likelihood—is probability. (The antonyms for these words are formed by attaching the prefix im-.) In addition, the adjective probabilistic applies to philosophical and scientific concepts pertaining, respectively, to competing options and to the supposed invalidity of certainty.
A subsequent post will detail the cognates proof and prove and other members of the probus family that deviate from the ancestral spelling.