matrix
A matrix is a table (or array) of numbers in rows and columns, for which addition, multiplication, etc., with similar tables is specially defined. For example, the matrix
| 1 | 2 | |
| 3 | 4 |
plus the matrix
| 5 | 20 | |
| 60 | 100 |
equals the matrix
| 6 | 22 | |
| 63 | 104 |
(Can you guess the rule defining addition?)
Calculations using matrices are useful in physics, engineering, psychology, statistics, etc. To add a square matrix of 100 terms in an array of 10 columns and 10 rows to another such matrix, 100 ordinary additions of numbers are needed. To multiply one such matrix by another, 1000 ordinary multiplications and 900 ordinary additions are needed. See references on matrix algebra and matrix calculus.