الفهرس 
1 IntroductionOnly 14 pages are availabe for public view
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Abstract
Functional differential equations (FDEs) are one of the classes of DEs in which oscillatory behavior is common. This type of equation deals with the presence of deviating arguments that express the previous and current times of the phenomenon. For more than 100 years, oscillation theory has been one of the most essential tools for studying the properties and behavior of solutions DEs. Therefore, this thesis, we are interested in studying the solution behavior of these equations. Specifically, the oscillation and nonoscillation of solutions, as well as deducing and improving some asymptotic and monotonic properties of the positive solutions, if any, for many different types of DEs, such as second and third-order DDEs and NDDEs.