from The American Heritage® Dictionary of the English Language, 4th Edition
- adv. Undoubtedly; definitely: This is certainly not my writing.
- adv. By all means; of course: You may certainly join us.
- adv. Surely: They certainly are hard workers.
from Wiktionary, Creative Commons Attribution/Share-Alike License
- adv. In a way which is certain; with certainty.
- adv. Without doubt, surely; of course.
- adv. An emphatic affirmative answer.
from the GNU version of the Collaborative International Dictionary of English
- adv. Without doubt or question; unquestionably.
from The Century Dictionary and Cyclopedia
- With certainty; without doubt or question; in truth and fact; without fail; inevitably; assuredly; undoubtedly; unquestionably; of a certainty.
from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
- adv. definitely or positively (`sure' is sometimes used informally for `surely')
certain + -ly (Wiktionary)