1：promise的主要意思是承诺，举例句 I will call you back，I promise.

2：ensure的主要意思是确保，保证，举例句 We tried to ensure that everyone got a fair deal.

3：assure的主要意思是使…确信，举例句Victory would assure a place in the finals.

4：declare的意思是宣布，申明，举例句：I declare this festival open.