In topology and combinatorics, it is common to glue together simplices to form a simplicial complex.
en.wikipedia.org At the secondary level, topics include algebra, geometry, conics, trigonometry, probability, combinatorics and calculus.
en.wikipedia.org The second part expands on enumerative combinatorics, or the systematic numeration of objects.
en.wikipedia.org His areas of research include combinatorics, randomness, pseudorandomness, information theory, communication complexity, computational complexity theory, quantum computation, quantum information science.
en.wikipedia.org His field of research was initially number theory, but he worked mainly in combinatorics and coding theory.
en.wikipedia.org