1. The problem asks: What is \( \varepsilon \)? 2. \( \varepsilon \) (epsilon) is a Greek letter commonly used in mathematics and science. 3. In mathematics, especially in calculus and analysis, \( \varepsilon \) often represents a very small positive number, used to describe limits and precision. 4. For example, in the definition of a limit, \( \varepsilon \) represents an arbitrarily small positive distance from a point. 5. In physics and engineering, \( \varepsilon \) can represent different quantities such as permittivity in electromagnetism. 6. Therefore, \( \varepsilon \) is a symbol, not a fixed number, and its meaning depends on the context. Final answer: \( \varepsilon \) is a Greek letter used to denote a small positive quantity or other context-dependent values.