TITLE: Holding Sequence of Variables Constant
QUESTION [0 upvotes]: I know that a zero subscript is a common way to notate a variable that is being held constant - e.g. $x_0$, as in $f(x_0, y)$. However, let's say we had a function of many variables, such as $$f(x_i, ..., x_n)$$ and we wanted to hold all variables except $x_i$ constant. Then, let's say we wanted hold all variables except for the second variable in the sequence constant. What is the best way to notate this for each variable in the sequence?

REPLY [0 votes]: The standard way is to put a hat over the variable not being held constant ;
 like $f(x_1,x_2 \ldots \widehat{x}_j \ldots x_n)$ would mean that the $j$-th variable is not held constant ,for example $f$ may be linear in the $j$-th variable with the other's fixed for each $j$ ;this called multi-linear .
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