$Assumption for multiple variables

Question

I want to restrict my variables to certain ranges for my entire notebook, is there a way I can do that in one go without entering a different $assumption line for every variable?

Edit: I want to define the domain of variables for all calculations in my notebook (googling helped me frame my needs better!)

Answer 1

Globally define as follows

$Assumptions = b >= 0 && c >= 0 && {u11, u13, u14} \[Element] Reals

then use globally defined variables as follows

Simplify[expression  with global variables]