Runtime error
Error that occurs during execution, not at compile time. Common types: NullPointerException, division by zero, TypeError, stack overflow, out of memory, network timeout.
Distinct from syntax errors (parser catches) and compile-time errors (type checker catches). Statically typed languages reduce runtime errors by moving them to compile time. Modern language design tries to minimize runtime traps: Rust eliminates NPE via Option<T>, Swift via Optionals, TypeScript strict mode requires explicit null checks. Exception handling (try/catch) is the standard pattern. Modern alternative: Result type (Rust, Haskell, modern Java with record patterns) makes errors explicit in the type signature.