doubt

1 doubt /ˈdaʊt/ verb
doubts; doubted; doubting
1 doubt
/ˈdaʊt/
verb
doubts; doubted; doubting
Britannica Dictionary definition of DOUBT
[+ object]
1 
: to be uncertain about (something) : to believe that (something) may not be true or is unlikely
2 
: to have no confidence in (someone or something)

— doubter

noun, plural doubters [count]
2 doubt /ˈdaʊt/ noun
plural doubts
2 doubt
/ˈdaʊt/
noun
plural doubts
Britannica Dictionary definition of DOUBT
: a feeling of being uncertain or unsure about something
[noncount]
— often + about
[count]
— often + about

beyond doubt

◊ If something is beyond doubt, it is definitely true.

in doubt

: in a state of being uncertain or unsure

no doubt

: without doubt or with very little doubt — used when you are making a statement that you think is certainly or almost certainly true

no doubt about it

— used to stress that something is true

the benefit of the doubt

— see 1benefit

without (a) doubt

— used to stress that something is true