Word family noun certainty ≠ uncertainty adjective certain ≠ uncertain adverb certainly ≠ uncertainly
From Longman Dictionary of Contemporary Englishldoce_711_zcertainlycer‧tain‧ly /ˈsɜːtnli $ ˈsɜːr-/ ●●● S1 W1 adverb [sentence adverb] 1 CERTAINLY/DEFINITELYwithout any doubt SYN definitely I certainly never expected to become a writer. They’re certainly not mine.it is certainly true/possible etc It is certainly true that there are more courses on offer. The girl was almost certainly murdered. ‘Not smoking has made a real difference.’ ‘It most certainly has.’2 AGREE spoken used to agree or give your permission ‘I’d like a beer, please.’ ‘Certainly, sir.’ ‘Can I come along?’ ‘Certainly.’3 → certainly notTHESAURUScertainly used when saying that you are sure about somethingAmy’s certainly growing, but she’s not gaining weight.It’s certainly not the cheapest way of getting to New York.‘Is this his signature?’ ‘Almost certainly.’undoubtedly used when saying that you are completely sure about something. Undoubtedly sounds more certain and a little more formal than certainlyThey are undoubtedly the better team.Undoubtedly it will be a huge shock for him. The furniture, although undoubtedly fashionable, was a little too plain for my taste.there is no doubt used when you are completely sure about somethingThere is no doubt that violence on TV influences children.He’s definitely innocent. There’s no doubt about that.without (a) doubt used when you are completely sure about somethingShe was without doubt one of Mexico’s finest artists.There would be, without a doubt, some perfectly ordinary explanation for his behaviour. Examples from the Corpus
certainly• Certainly, a backpacking trip in the high Sierras is not for everyone.• We're certainly a lot better off than we were five years ago.• And that was certainly a start.• Books and people certainly affected him.• We are not especially well-treated, certainly not as well as the locals.• Not the papers or the magazines and certainly not Kylie.• Should the man choose to chase the quail rather than shoot it, he would almost certainly still have his dinner.• This thought now struck him as too simple and certainly unpleasant in its snobbery, and he tore it up.• And that she most certainly was not, she told herself adamantly.• And it certainly Was, though not in the way the interviewees assumed.it is certainly true/possible etc• I am glad that Kay accepts the appeal of the ideal of environmental triggering: it is certainly true.• With Michael Barry, it is certainly possible.• More neutrally it is certainly true that the range of courses we offer continues to increase.• And it is certainly true that these earnings differentials have had a tendency to diminish in the past.• Yet, it is certainly possible to argue Arden is as dramatically interesting. 