What is type safety?

Example: You have a field in your project tracker labeled 'priority.' Without a type constraint, someone enters 'high,' another enters '1,' a third enters 'ASAP,' and a fourth enters the color red. The field becomes useless — not because people are careless, but because unconstrained fields accept anything, including nonsense. Add a type (e.g., enum: critical | high | medium | low) and the field rejects invalid inputs before they pollute your system.

This concept is part of Classification and Typing in the How to Think curriculum, which builds the epistemic infrastructure for classification and typing.