conjecture

I’ve told you all I know myself now, for the rest is mere surmise and conjecture.

His quiet self-confident manner convinced me that he had already formed a theory which explained all the facts, though what it was I could not for an instant conjecture.

There was the dead dog, however, to prove that his conjecture had been correct.

As they walked across the lawn towards the river, Elizabeth turned back to look again; her uncle and aunt stopped also; and while the former was conjecturing as to the date of the building, the owner of it himself suddenly came forward from the road which led behind it to the stables.