suppositious

Supposititious is an English adjective used to describe something that is assumed or supposed to be real but is not genuine. It can refer to fictitious or counterfeit objects, claims, or persons presented as authentic, as well as to propositions or hypotheses that are hypothetical rather than proved.

Etymology and form: the word derives from Latin suppositus, a past participle of supponere, and entered English through Latin and French. The standard spelling in modern usage is supposititious; suppositious is a less common variant that some dictionaries recognize or note as alternative spelling.

Usage and nuance: supposititious tends to appear in scholarly, historical, or literary contexts. It is commonly used in discussions of genealogy, law, or documentary evidence to signal doubt about authenticity—for example, a supposititious heir or a supposititious document. The term conveys a sense of something claimed to be genuine but lacking substantiation, rather than merely uncertain or disputed.

Relation to related terms: supposititious is often contrasted with genuine, authentic, or verifiable, and with fictitious or spurious when emphasizing lack of real basis. It shares semantic space with hypothetical when referring to ideas or propositions, though the latter focuses more on assumed conditions rather than authenticity.

See also: spurious, fictitious, hypothetical, fraudulent, authentic. Note that supposititious is relatively formal and infrequently used in everyday language.