adverb

certainly

Without doubt; also used to express definite agreement.

The new lights certainly make the room brighter.

Etymology

Latin certus meant settled or sure. Certainly turns that firmness into a statement made without doubt, and in replies it conveys equally firm agreement.

More examples

  • We certainly need more time to finish this project.
  • “May I sit here?” “Certainly, please do.”
  • The repair certainly costs less than a new refrigerator.

Forms

certainly

certain adjective — Sure that something is true or correct.

certainty noun — The state of being free from doubt.

Similar words

definitely
Emphasizes a firm conclusion or commitment with no hesitation.
undoubtedly
Stresses lack of doubt rather than expressing direct agreement.