What is the difference between the terms "Margin" & "Mark-up" ?

in my opinion; the margin is a percentage or amount reflects the total profit per unit of production that added to the unit cost, where the markup is an amount or a percentage that could be a part of the margin of included into the unit cost. the markup is set to cover a specific item such as; sales tax (when selling price is included the sales tax), sales commission, sales order carrying out cost ...etc. generally it is an incidental cost.