Low-dimensional topology Algebraic topology -- Classical topics -- Degree, winding number 1 Algebraic topology -- Homology and cohomology theories -- Other homology theories 1 Combinatorial topology 1 Differential topology 1 Group theory and generalizations -- Other generalizations of groups -- Loops, quasigroups 1 Group theory and generalizations -- Other generalizations of groups -- Sets with a single binary operation (groupoids) 1 Group theory and generalizations -- Permutation groups -- General theory for finite groups 1 Knot theory 1 Manifolds and cell complexes -- Low-dimensional topology -- Fundamental group, presentations, free differential calculus 1 Manifolds and cell complexes -- Low-dimensional topology -- Invariants of knots and 3-manifolds 1 Manifolds and cell complexes -- Low-dimensional topology -- Knots and links in $S^3$ 1 Manifolds and cell complexes -- PL-topology -- Knots and links (in high dimensions) 1 Topological manifolds 1