Functions in Everyday Math

Every formula you have ever used is a function. "Dose in mg = body weight × 0.5" maps weight to a dose. "Sales tax = subtotal × 0.08" maps a subtotal to tax. Each one takes a number in, applies a rule, and hands you exactly one number back. Functions are the grammar of math.

Programming is essentially function composition. Every Excel column of computed values is a function of another column. When you ask an AI a question, the model's weights define a giant function that maps your text to its answer.