Diagram algebras

graph whose edges are labelled with irreducible representations of a compact Lie group and whose vertices are associated with intertwiners of the edge representations adjacent to it

Begriffsschrift (German for, roughly, "concept-writing") is a book on logic by Gottlob Frege, published in 1879, and the formal system set out in that book.

mathematical concept in knot theory

knot invariant

graphical notation for multilinear algebra calculations

Relation between triples of links differing by 1 crossing, used to define knot invariants