The expression "√4" represents the square root of the number 4. The square root of a number is a value that, when multiplied by itself, gives the original number. In this case, since 2 × 2 = 4, the square root of 4 is 2. Square roots are commonly used in mathematics and can be found in various fields, including geometry, algebra, and statistics. The symbol "√" is called the radical sign, and it indicates that we are looking for a number that satisfies the square root condition.