This monograph develops projective geometries and provides a systematic treatment of morphisms. It is unique in that it does not confine itself to isomorphisms. This work introduces a new fundamental theorem and its applications describing morphisms of projective geometries in homogeneous coordinates by semilinear maps. Other topics treated include three equivalent definitions of projective geometries and their correspondence with certain lattices; quotients of projective geometries and isomorphism theorems; recent results in dimension theory; morphisms and homomorphisms of projective geometries; special morphisms; duality theory; morphisms of affine geometries; polarities; orthogonalities; Hilbertian geometries and propositional systems. The book concludes with a large section of exercises. Audience: This volume will be of interest to mathematicians and researchers whose work involves projective geometries and their morphisms, semilinear maps and sesquilinear forms, lattices, category theory, and quantum mechanics. This book can also be recommended as a text in axiomatic geometry.