Answer
Thread safety means code preserves its documented invariants when used concurrently as allowed. • Shared mutable state needs synchronization, atomic operations, immutability, or confinement. • A type is not automatically thread-safe merely because individual operations appear small. • Document whether instances, static members, enumeration, and callbacks support concurrent use.
💡 C# Example
private int count;
void Increment() => Interlocked.Increment(ref count);
⚡ Quick Revision
Thread-safe code coordinates shared state under its documented concurrency contract.