5×1

5×1 is a mathematical expression read as “five by one.” In basic arithmetic, it denotes the product of the numbers five and one, which equals five. Because multiplication is associative and the number one acts as the multiplicative identity, 5×1 = 5 and 1×5 = 5.

In linear algebra and matrix terminology, 5×1 often describes a matrix dimension: a matrix with 5 rows and 1 column. Such a 5×1 object is a column vector of length five. It can be written as a vertical arrangement of five elements, for example [a1; a2; a3; a4; a5]. The transpose of a 5×1 matrix is a 1×5 matrix, i.e., a row vector with five elements. Column vectors of this size are frequently used to represent quantities in five-dimensional space or to stack multiple scalar values into a single data structure.

Context matters for the meaning of 5×1. As a numeric expression, it produces the scalar 5. As a description of an array or data structure, it specifies a 5-by-1 layout, indicating five entries arranged in a single column. In both interpretations, the symbol × conveys the idea of a product or a dimensional form, and the precise interpretation depends on the mathematical or applied setting.