Unpaired Word

An unpaired word is one that, according to the usual rules of the language, would appear to have a related word but does not. Such words usually have a prefix or suffix that would imply that there is an antonym, with the prefix or suffix being absent or opposite.

Unpaired words can be the result of one of the words falling out of popular usage, or can be created when only one word of a pair is borrowed from another language, in either case yielding an accidental gap, specifically a morphological gap. Other unpaired words were never part of a pair; their starting or ending phonemes, by accident, happen to match those of an existing morpheme, leading to a reinterpretation.

The classification of a word as "unpaired" can be problematic, as a word thought to be unattested might reappear in real-world usage or be created, for example, through humorous back-formation. In some cases a paired word does exist, but is quite rare or archaic (no longer in general use).

Such words – and particularly the back-formations, used as nonce words – find occasional use in wordplay, particularly light verse. There are a handful of notable examples in modern English – three poems and one short story.