most important; main最重要的；主要的◆Tourist revenue is now our principal source of wealth.旅游收入目前是我们的主要财源。◆the principal markets for our products我们产品的主要市场 () relating to an original amount of money that is lent or invested, rather than any interest本金的；资本的◆The total interest is now more than the principal amount.利息总额现已超过本金。