In mathematics, brackets usually represent vectors, matrices or sets, such as [1, 2,3] representing a three-dimensional vector, [2 3; 4 5] represents a 2x2 matrix, and {1, 2,3} represents a set. However, solid brackets usually indicate the interval of numbers, such as [3,7] indicating a closed interval containing 3 and 7, and (3,7) indicating an open interval excluding 3 and 7.