to be sure Definition

sure
adj surer, surest

1. Confident beyond doubt in one's belief or knowledge; convinced.

Example: felt sure he'd picked up the keys
Thesaurus: confident, positive, assured, convinced, certain, definite, secure; Antonym: doubtful, wavering.
2. Undoubtedly true or accurate.

Example: a sure sign
3. Reliably stable or secure.

Example: on a sure footing

adverb

1. colloq
Certainly; of course.

Idiom: as sure as eggs is eggs (as sure as eggs are eggs)

Without the remotest doubt.

Idiom: as sure as fate (sure as fate)

Inevitably.
Example: put the washing out and, as sure as fate, down came the rain

Idiom: be sure and

To make certain to (do something).
Example: Be sure and phone when you get there

Idiom: be sure of something

To be unquestionably certain or assured of it.
Example: wanted to be sure of the train times

Idiom: be sure of oneself (feel sure of oneself, be very, so etc sure of oneself)

To act in a very self-confident way.

Idiom: be sure that

To be convinced that.
Example: I was sure that we'd agreed to meet on Friday

Idiom: be sure to

To be guaranteed or certain to (happen, etc).
Example: Whenever we plan a picnic it's sure to rain

Idiom: for sure

colloq
Definitely; undoubtedly.

Idiom: make sure

To take the necessary action to remove all doubt or risk.
Thesaurus: determine, fix, guarantee, establish.

Idiom: sure enough

colloq
In fact; as was expected.

Idiom: to be sure

Certainly; admittedly.

Derivative: surenesss
noun

Etymology: 14c: from French sur, from Latin securus without care.