The term "block" is used in mathematics for a distinguished constituent of a larger structure, with its precise meaning determined by context.
In design theory, the blocks of a block design are distinguished subsets of its point set.
In graph theory, a graph block is a maximal connected subgraph without an articulation vertex.
In combinatorics, a set block is one of the subsets comprising a set partition.
For a group action, a group block is a subset that is either preserved by each group element or mapped disjointly from itself.
In linear algebra, the smaller matrices comprising a block matrix are called blocks.
A digit block is a consecutive string of digits in a numeral.
