Multiply, then add

Say the inputs are 2, 1, and 3. The weights are 0.5, 0.2, and 0.1.

The neuron multiplies each pair, then adds the results:

2 × 0.5 + 1 × 0.2 + 3 × 0.1 = 1.5

If the threshold is 1.4, it fires. If the threshold is higher, it stays quiet.

That's what a neuron does. Mathematicians write it as x₁w₁ + x₂w₂ + x₃w₃ — x for input, w for weight — but the letters aren't the point. The operation is.

This formula shows up everywhere in AI. Every artificial neuron in every network does exactly this. That's why it's worth seeing once.