verb (v)

• make certain of(verb.communication)

  Example:
  This nest egg will ensure a nice retirement for us.
  

  Synonym:
  assure, guarantee, insure, secure
  

  source: wordnet30
• be careful or certain to do something; make certain of something(verb.cognition)

  Synonym:
  ascertain, assure, check, control, insure, see, see to it
  

  source: wordnet30
• To make sure. See Insure.(verb)

  source: webster1913