v = Subscript[v, 0]*Sin[(Pi*S)/Subscript[S, 0]]; a = dv/ds v; a = D[v, s]
$RecursionLimit::reclim: Recursion depth of 256 exceeded.
Reference in the link shown by error msg doesn't give me a relief. I'm assuming the root cause is that I'm not assigning concrete values to the variables. But here I want to operate differentiation w/o assigning values (is there explicit name in math for this kind of operation?). Don't even know if it's differentiation specific or general issue for an operation not assigning concrete values (and thus can't assign proper tags to this question either). I haven't been able to find the corresponding reference. Thanks.
Update) Code @acl gave works for me now. However, I'm just curious why my code returns the same error even after I corrected "S" to "s", and also removed 2nd line which I didn't really expect
Mathematica to do anything for.