no doubt
What is the opposite of no doubt? Here is what we hold, with its meaning and related words.
Adverb — Very probably; used to show that the speaker assumes something is true without being able to prove it.
How to use no doubt
The word patterns that sound natural to a native speaker.
The adverb is neutral and common in writing; the one-word agreement use is casual speech only.
Etymology
Inherited from Middle English ne doute, a calque of Old French saunz doute, itself borrowed unadapted into Middle English.
Full origin of no doubt →