The present work of the book is devoted to the study of fixed point theorems in complete metric spaces, metrically convex spaces, symmetric spaces, non-Archimedean Menger PM-spaces, fuzzy metric spaces, normed linear spaces and Banach spaces under different contractive conditions and weaker forms of commutativity for single-valued and multivalued mappings. The book ends with some fixed point theorems by using iterative procedures.