If both p and q are variables, then the coefficient is -7
If p is a constant and q a variable then the coefficient of q is -7p
If q is a constant and p a variable then the coefficient of p is -7q
If both p and q are constants then we could say that the coefficient of the 0th power of some variable x^0 (say) is -7pq, but we would usually simply describe -7pq as a constant term.