What’s the meaning of “;” in $f(x;\theta)$?2
A value that is already “built in” to a function.
Example: imagine a function that works out the height of a tree1:
h(year) = 20 × year
then “20” is a parameter.
Parameters can be changed so that the function can be used for other things.
Example: A different tree’s growth rate is 30 cm per year, so its function is h(year) = 30 × year
We could even make it more general by writing
h(age; rate) = rate × age
and in this case a semicolon (;) is used to separate the variable(s) from the parameters(s)
2. https://math.stackexchange.com/questions/342268/what-does-the-semicolon-mean-in-a-function-definition ↩