2x1

2x1, read as “two by one,” is a term used across mathematics, geometry, and design to denote a specific dimension, a matrix size, or a product of numbers. Its precise meaning depends on the context in which it appears.

As a dimension, 2×1 indicates a rectangle that is two units tall and one unit wide. In planning drawings, manufacturing, or photography, it often appears as shorthand for such measurements. The explicit aspect ratio is 2:1, describing the proportional relationship between height and width.

In linear algebra, a 2×1 object is a column vector with two rows, typically written as [a; b]. It has two components and is the result of multiplying a 2×1 matrix by a compatible matrix or vector. Its transpose is a 1×2 row vector.

In combinatorics and tiling, a 2×1 domino tile covers exactly two adjacent unit squares. Domino tilings of boards are a well-studied topic in mathematics, with applications in statistical mechanics and algorithmic counting.

In arithmetic, the expression 2×1 denotes the product of 2 and 1, equal to 2.

Notes: the term is sometimes abbreviated as “2x1” in specifications, and context is important to interpret it correctly.