Synonyms for sure

adjective

• having or feeling no doubt or uncertainty; confident and assured
• certain to occur; destined or inevitable
• impossible to doubt or dispute
• exercising or taking care great enough to bring assurance
• reliable in operation or effect
• (of persons) worthy of trust or confidence
• certain not to fail
• infallible or unfailing
• physically secure or dependable

adverb

• definitely or positively (`sure' is sometimes used informally for `surely')