sure
I
 /ˈʃɚ, Brit ˈʃɔː/  adj  , sur·er, -est [also more ~; most ~]
  1 not used before a noun : not having any doubt about something : convinced or certain
   I am sure (that) everything will be fine.
   We are quite/completely sure (that) we will be finished on time.
   She's not sure who will be there.
   Are you sure you want to go?
   Are you sure about that?
   She'll be there, I'm sure of it.
   Are you sure of the results?
  2 : not allowing any doubt or possibility of failure
   The return of the robins is a sure sign of spring.
   The letter is a sure indication that she cares.
   Pizza is a sure crowd pleaser.
   The surest way to lose weight is with diet and exercise.
   One sure way to improve your health is to stop smoking.
   He's a sure bet to receive the award. [=he's sure/certain to receive the award]
   It's a sure thing that they'll win. [=it is certain that they'll win]
   Flowers and chocolates are always sure things [=people always like to be given flowers and chocolates], but consider giving your wife something different this year.
  — see also SURE THING ((BELOW))
  3 — used to say that something will definitely happen or that someone will definitely do something;
  — usually followed by to + verb
   It's sure to be a great party.
   I'll be sure to call when I get home.
   They are sure to win.
   Her latest movie is sure to make you laugh.
   Whatever you say, he's sure to disagree with you.
  4 : known to be true or correct
   What is sure [=definite, indisputable] is that they have a problem, and we have the means to fix it.
   Nothing else is sure.
   One thing is (for) sure, we'll never eat there again. [=we certainly will never eat there again]
  5 a : firm or solid
   a sure hold/grip
   a hiking boot that provides sure footing [=that helps to keep your foot from slipping]
  — often used figuratively
   He lacks a sure grasp of the issue. [=he does not understand the issue well]
   She has a sure command of the French language.
  5 b : calm, steady, and confident
   the sure hands of a surgeon
  be sure
    — used to tell someone not to forget to do something
    Be sure to lock the door when you leave.
   
  for sure
   : without a doubt : definitely or certainly
    No one knows for sure [=for certain] what happened.
    That was a mistake for sure. = That for sure was a mistake.
    (US, informal) “Do you want to come to the party?” “For sure.” [=I certainly do]
    “We don't want that to happen again.” “That's for sure!” [=that is certainly true]
  make sure
   : to find out or do something so that you have no doubt about whether something is true, correct, will happen, etc.
    Make sure (that) you turn the oven off.
    Remember to make sure (that) all the doors are locked.
    They made sure everyone knew where they were supposed to be.
    Make sure it doesn't happen again.
  sure of yourself
   1 : confident in your abilities
    He was never very sure of himself as a comedian.
   2 somewhat disapproving : overly confident or arrogant
    They seem awfully sure of themselves.
  sure thing
    informal  
    — used to say “yes” or to agree to a request or suggestion
    “Can you be here in five minutes?” “Sure thing.”
    see also sure 2 (above), 1
  to be sure
    formal  
    — used to say that you admit that something is true
    It will be challenging, to be sure, but I am confident that we will succeed.
   
————————
II
  adv  
   informal  
  1 a
  — used to say “yes” or to agree to a request or suggestion
   “Can you help me with this?” “Sure.” [=certainly]
  1 b
  — used to disagree with a negative statement or suggestion
   “I don't think he's coming.” “Sure he is. He's just a little late.”
   “Don't you like popcorn?” “Sure I like popcorn. I just don't want any right now.”
  2
  — used to emphasize that you agree with the first part of the statement that you are about to make
   Sure, she's very talented, but other factors could limit her success.
  3 US
  — used as an informal way to accept someone's thanks
   “Thank you for your help.” “Sure.” [=you're welcome]
  4 US
  — used for emphasis
   I sure am tired.
   This sure beats working.
   “Do you want to come?” “I sure do!”
   (impolite) I sure as hell hope you know what you're doing!
  sure enough
    — used to say that what happened was not surprising or unexpected
    We were finally ready to go outside, and sure enough, it started to rain.