Adivar M.Islam M.N.Raffoul Y.N.2023-06-162023-06-1620121303-5010https://search.trdizin.gov.tr/yayin/detay/131958https://hdl.handle.net/20.500.14365/4567In this study, we employ the fixed point theorem of Krasnoselskii and the concepts of separate and large contractions to show the existence of a periodic solution of a highly nonlinear delay differential equation. Also, we give a classification theorem providing sufficient conditions for an operator to be a large contraction, and hence, a separate contraction. Finally, under slightly different conditions, we obtain the existence of a positive periodic solution.eninfo:eu-repo/semantics/closedAccessKrasnoselskii's fixed point theoremLarge contractionPeriodic solutionPositive periodic solutionSeparate contractionTotally nonlinear delay differential equationsArticle2-s2.0-84866030377