Does post-structuralism, relativism and postmodernism not basically representent the same way of thinking?

Same goes with structuralism and modernism i suppose. I get the sense that postmodernism is used to interpret art or litterature, relativism is used in psychological descriptions and post-structuralism is more or less same as postmodernism; all stating that truth is not universal, but rather a product of the individual or the individual group. Yay or nay? Thanks in advance