Kenneth G. Wilson (1923–). The Columbia Guide to Standard American English. 1993.
obverse, converse, inverse, reverse (adjs., nn. )
The -verse part of these words means “to turn,” and the prefixes suggest the direction or nature of the turn involved. Obverse means “turned toward you” and hence “the front,” as in The obverse side of the coin is the heads side. As a noun, the obverse is the opposite of the reverse, both generally used of coins and medals: Tails is the reverse [side] of a coin. Inverse means “opposite” or “upside down,” as in an inverse ratio. The inverse of a proposition is its opposite. A converse proposition or theorem is one reversed in order or meaning, and the converse is such a reversed proposition or theorem: Having demolished his proposition, I will now prove the converse.
