1con·jec·ture /kənˈʤɛktʃɚ/ noun plural con·jec·tures
an opinion or idea formed without proof or sufficient evidence : guess
] ▪ The biography includes conjectures about the writer's earliest ambitions. ▪ a conjecture about the extent of the injury
] ▪ Your plan is based on (nothing more than) conjecture. ▪ Most of the book is conjecture, not fact. ▪ The criminal's motive remains a matter of conjecture. [=people can only guess about the criminal's motive; no one knows the criminal's motive]
— con·jec·tur·al /kənˈʤɛktʃərəl/ adjective
[more conjectural; most conjectural
▪ Most of the book is conjectural.