Introduction:
Surds and indices are mathematical concepts that are used to represent and manipulate numbers. They have distinct characteristics and serve different purposes in quantitative aptitude.

Surds:
Surds are irrational numbers that cannot be expressed as a ratio of two integers. They are typically represented in the form √n, where n is a non-perfect square. Surds are used to represent numbers that have non-recurring and non-terminating decimal expansions. Some key points about surds are:

- Surds are expressed using the square root symbol (√).
- Surds can be simplified but not exactly evaluated unless they are perfect squares.
- Surds can be added, subtracted, multiplied, and divided using certain rules.
- Examples of surds include √2, √3, and √5.

Indices:
Indices, also known as exponents or powers, are used to represent repeated multiplication of a number by itself. They are written as a superscript number attached to the base number. Some key points about indices are:

- Indices are expressed using the caret symbol (^).
- Indices can be positive or negative, indicating whether the base number is multiplied or divided repeatedly.
- Indices can be added, subtracted, multiplied, and divided using specific rules.
- Examples of indices include 2^3 (2 raised to the power of 3), 5^(-2) (5 raised to the power of -2), and 10^0 (any number raised to the power of 0 is equal to 1).

Differences:
The main differences between surds and indices can be summarized as follows:

1. Representation: Surds are represented using the square root symbol (√), while indices are represented using the caret symbol (^).

2. Type of Numbers: Surds represent irrational numbers, while indices can represent rational and irrational numbers.

3. Simplification: Surds can be simplified, whereas indices can be evaluated to obtain a specific value.

4. Arithmetic Operations: Surds can be added, subtracted, multiplied, and divided using specific rules, while indices follow their own rules for arithmetic operations.

Conclusion:
Surds and indices are distinct mathematical concepts used in quantitative aptitude. Surds represent irrational numbers and are expressed using the square root symbol, while indices represent repeated multiplication of a number and are expressed using the caret symbol. Understanding the differences between these concepts is crucial for solving problems involving surds and indices effectively.