SESKStuff Everyone Should Know
SESK: Stuff Everyone Should Know · sesk.info/ai-relu-max-zero

What does the ReLU activation return for an input x?

ReLU returns max(0, x).

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  1. max(0, x) ✔
  2. 1 divided by x
  3. x squared

Why: Negative inputs become zero. Zero and positive inputs pass through unchanged, making ReLU simple and piecewise linear.

Huh, didn't know that: ReLU has slope 1 on its positive side and slope 0 on its negative side.

The dad joke
ReLU stays positive, but only when the input does.
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References

Answer: max(0, x). Negative inputs become zero. Zero and positive inputs pass through unchanged, making ReLU simple and piecewise linear.

  1. Google Machine Learning Crash Course: Activation functions developers.google.com/machine-learning/crash-course/neural-networks/activation-functions
    is greater than or equal to 0, return the input value.
    Checked 2026-10-11.

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