T-Shirt sizes? > Without a numerical value, such estimates cannot be misused easily in mathematical formulas. Those units will still be misused and even abuse

T-Shirt sizes? > Without a numerical value, such estimates cannot be misused easily in mathematical formulas. Those units will still be misused and even abused. "What does an M mean in days?", you'll be asked. And voila, there's a number. And, if there's a number there's some equation in which it'll be used.