# Why is an activation function notated as “g”?

In many cases an activation function is notated as g (e.g. Andrew Ng's Course courses), especially if it doesn't refer to any specific activation function such as sigmoid.

However, where does this convention come from? And for what reason did g start to be used?

• It’s just a notation. You can call it whatever you want. a BC d – Vivek Khetan Nov 3 '17 at 12:25
• Yes but what is the reason? That is the point of my question. – Blaszard Nov 3 '17 at 13:12
• Read some linear algebra. – Vivek Khetan Nov 3 '17 at 13:30
• That is not an answer. – Blaszard Nov 6 '17 at 10:03
• ESL uses $\sigma(.)$. This is a dumb question. – generic_user Nov 6 '17 at 21:37

• He didn't write the hypothesis function as h; he used z. So it was not intuitive for me why he used g... – Blaszard Nov 9 '17 at 19:28