This lecture covers alternative definitions of the determinant, starting with a reminder of the definition of det (a) and exploring various ways to describe it. The lecture delves into the properties of determinants, including the invertibility of matrices and the relationship between det (a) and det (a-1). It also discusses the implications of linearly dependent columns on the determinant value. The geometric interpretation of determinants and the Gauss algorithm for determinant calculation are explained, along with examples demonstrating the application of these concepts.