Variable
A letter or symbol standing in for an unknown or changing number.
- x, y, z for inputs/outputs; a, b, c for constants.
- θ, β for parameters in stats and ML.
- Symbolic reasoning is the leap from arithmetic to algebra and ML.
When to use: Any formula or model definition where values can vary.
Example: y = w·x + b: w (weight) and b (bias) are learned; x (input) given; y computed.