What is the meaning of the semicolon in $h(x;\theta)$?

Question

The context is machine learning, and the full expression is $h(x;\theta) = \operatorname{sign}(\theta_1 x_1 + \cdots + \theta_d x_d)$. $x$ is a feature vector and $\theta$ parameterizes a set of classifiers. I don't understand why the semicolon was used instead of the comma I would expect. Does it add meaning to the definition of $h$?

Answer 1

It is just like a comma. A semicolon is used sometimes to emphasize the fact that different variables play different roles. In your example, the xs are felt like normal variables while the thetas are more like parameters to the function.