to be sure

sure  (shr, shûr)

adj. sur·er, sur·est

1. Impossible to doubt or dispute; certain.

2. Not hesitating or wavering; firm: sure convictions.

3. Confident, as of something awaited or expected: sure of ultimate victory.

4.

a. Bound to come about or happen; inevitable: sure defeat.

b. Having one's course directed; destined or bound: sure to succeed.

5. Certain not to miss or err; steady: a sure hand on the throttle.

6.

a. Worthy of being trusted or depended on; reliable.

b. Free from or marked by freedom from doubt: sure of her friends.

7. Careful to do something: asked me to be sure to turn off the stove.

8. Obsolete Free from harm or danger; safe.

adv. Informal

Surely; certainly.

Idioms:

for sure Informal

Certainly; unquestionably: We'll win for sure.

make sure

To establish something without doubt; make certain: Make sure he writes it down.

sure enough

As one might have expected; certainly.

to be sure

Indeed; certainly.

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[Middle English, from Old French, safe, from Latin scrus; see secure.]

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sureness n.

Synonyms: sure, certain, confident, positive
These adjectives mean feeling or showing no doubt. Sure and certain are frequently used interchangeably; sure, however, is the more subjective term, whereas certain may imply belief based on experience or evidence: "Never teach a child anything of which you are not yourself sure" (John Ruskin). "In this world nothing is certain but death and taxes" (Benjamin Franklin).
Confident suggests assurance founded on faith or reliance in oneself or in others: The senator is confident of reelection.
Positive suggests full, emphatic certainty: The prosecutor had positive proof of the defendant's guilt. See Also Synonyms at certain.

Thesaurus

Adv.

1.

to be sure - admittedly; "to be sure, he is no Einstein" no doubt, without doubt