You think backwards... Using marks to buy materials = Spending [i][u]Marks[/u][/i] for [b][u]Materials[/u][/b] or Marks for Materials Using materials to buy marks = Spending [i][u]Materials[/u][/i] for [b][u]Marks[/u][/b] or Materials for Marks You can play games with semantics if that's something that makes you happy, but it won't change their meaning.