From Longman Dictionary of Contemporary Englishsincerelysin‧cere‧ly /sɪnˈsɪəli $ -ˈsɪr-/ ●○○ adverb 1 REAL/NOT FALSE OR ARTIFICIALif you feel or believe something sincerely, you really feel or believe it and are not just pretending SYN truly I sincerely hope I’ll see her again. We are sincerely grateful for your help.2 → (yours) sincerely
Examples from the Corpus
sincerely• But was it not possible that Tutilo had believed just as sincerely?• Steve sincerely believed he was doing the right thing.• The wrinkled child of a warrior culture, Aeschylus may have sincerely believed that Marathon represented his finest hour.• I sincerely hope that he retains his position.• I do want to tell you quite simply and sincerely how much I look forward to that.• We sincerely regret any trouble this has caused.• Some fathers sincerely tried to become parents, sharing the home workload and parental responsibilities.From Longman Business Dictionarysincerelysin‧cere‧ly /sɪnˈsɪəli-ˈsɪr-/ adverb Yours sincerely British English Sincerely yours American English an expression used to end a formal letter. You use this expression when you have addressed the person you are writing to by name, rather than Dear Sir or Dear Madam → compare faithfully 