Accidental gap
In linguistics an accidental gap, also known as a gap, paradigm gap, accidental lexical gap, lexical gap, lacuna, or hole in the pattern, is a potential word, word sense, morpheme, or other form that does not exist in some language despite being theoretically permissible by the grammatical rules of that language. For example, a word pronounced /zeɪ̯k/ is theoretically possible in English, as it would obey English phonological rules, but does not currently exist.