Review of Axiomatic Set Theory. Relation, Partial Ordering, Chain, Isomorphism, Cofinality. Ramsey Theorems, Partitions, Combinatorial Principles. Good and Bad Sequence, Finitely Free Partial Ordering, Well Partial Ordering, Ideal, Tree, Dimension. Embeddability Between Partial or Total Orderings. Scattered Chain, Neighborhood, Indecomposability. Use of Scattered Chains for the Study of Finitely Free and Well Partial Orderings. Barrier, Barrier Sequence, Forerunning, Embeddability Theorem for Scattered Chains, Better Partial Ordering. Isomorphism and Embeddability Between Relations, Local Isomorphism, Free Interpretability, Constant Relation, Chainable and Monomorphic Relation. Age, Rich Relation, Inexhaustible Relation, Saturated Relation, Existence Criterion for a Rich Relation of a Given Age. Homogeneous Relation, Relational System, Connection with Permutation Groups, Orbit. Bound of a Relation; Well Relation, Reassembling Theorem. Bibliography. Index.