doubt

To be undecided about; to lack confidence in; to disbelieve, to question.

He doubted that was really what you meant.

I had no wish to go, though I doubt if they would have noticed me even if I had.

To harbour suspicion about; suspect.

I walk by the Rule of my Maſter, you walk by the rude working of your fancies. You are counted thieves already, by the Lord of the way; therefore, I doubt you will not be found true men at the end of the way.

Rushing to the door of the church, [Robert the] Bruce met two powerful barons, [Roger de] Kirkpatrick of Closeburn, and James de Lindsay, who eagerly asked him what tidings? "Bad tidings," answered Bruce, "I doubt I have slain [John] Comyn." "Doubtest thou?" said Kirkpatrick, "I make sicker" (i.e. sure.) With these words, he and Lindsay rushed into the church, and dispatched the wounded Comyn.

To anticipate with dread or fear; to apprehend.

The rest of his horsemen the Duke sent to his campe, bicause they heard a great noise there, and doubted the enimies sally, and indeede they had issued foorth thrise, but were alwaies repulsed, especially through the valiantns of the English men that the Duke left there behind him [...]

Fear naught—nay, that I need not say— / But—doubt not aught from mine array. / Thou art my guest;—I pledged my word / As far as Coilantogle ford: [...]

To fill with fear; to affright.

I'll tell ye all my fears, one ſingle valour, / the vertues of the valiant Caratach / more doubts me then all Britain: [...]

To dread, to fear.

Edmond aþelstones broþer · after him was king · / Godmon & doutede · god þoru alle þing ·

Whilome in youth, when flowred my ioyfull ſpring, / Like ſwallow ſwift I wandred here and there: / For heat of heedleſſe luſt me ſo did ſting, / That I of doubted daunger had no feare.

Disbelief or uncertainty (about something); (countable) a particular instance of such disbelief or uncertainty.

There was some doubt as to who the child's real father was.

I have doubts about how to convert this code to JavaScript.

A point of uncertainty, especially a yes/no or a multiple-choice question

Ma'am, I have a doubt about today's lecture

It is entirely normal to hear a statement like "I have just one doubt, miss" or "If you have any doubts before the exam tomorrow, come see me in the staff room". The doubts in the aforementioned sentences are not as much rooted in a lack of faith as in a lack of understanding.