The notation ℚ(√2) represents a mathematical concept known as a field extension. Specifically, it is the set of all numbers that can be formed by taking rational numbers from the set ℚ and adding or multiplying them with the square root of 2. This means that any number in ℚ(√2) can be expressed in the form a + b√2, where a and b are rational numbers. In this context, ℚ is the field of rational numbers, which includes fractions like 1/2 and 3/4. The square root of 2, denoted as √2, is an irrational number, meaning it cannot be expressed as a simple fraction. The field ℚ(√2) thus contains both rational numbers and combinations of these with √2, expanding the number system to include new values.