the truth
Synonym discussion
Sense: idiom/1
'The truth' refers to what is actually the case, as opposed to what is false, assumed, or fabricated. 'The facts' are specific pieces of verified information — you can list facts, but truth is the broader picture made up of those facts (the truth about a crime includes many facts, but also context and motive). 'Reality' is the widest term, covering everything that exists regardless of whether it can be verified or stated. 'The honest truth' (informal) adds emotional emphasis, often used when persuading someone: 'The honest truth is I was too scared to go.' Use 'truth' when contrasting with lies or deception; use 'facts' when contrasting with opinions or guesses; use 'reality' when contrasting with imagination or hope.
Etymology
The noun 'truth' comes from Old English 'trēowþ' meaning 'fidelity, faith, pledge', from Proto-Germanic '*trewwō' ('faith, pledge'). The fixed phrase 'the truth' has been used since Old English times to refer to the state of being in accordance with fact or reality, as opposed to falsehood. Modern usage as a set phrase ('tell the truth', 'the truth about') became fully established by the 14th century.