We consider the geometric structure of quasi-normed Calderón–Lozanovskiĭ spaces. First, we study relations between the quasi-norm and the quasi-modular “near zero” and “near one,” which are fundamental for the theory. With their help, we provide a precise description of the basic monotonicity properties. In comparison with the well-known normed case, we develop a number of new techniques and methods, among which the conditions