certify, rectify, testify, verify
这是一组形近易混词。

certify v.证明，声称是真的。
He certified it was his wife's handwriting.             
他证明那是他妻子的手迹。
 
rectify v.改正，纠正；整顿。
He rectified the mistake in the contract by changing its wording.    
他通过改变措辞纠正了合同里的错。

testify  v. (在法庭上)宣誓作证；表明。
He is the only person who can testify in this case, because the other witnesses were killed mysteriously.
由于其他的证人已经被神秘地杀害，他成为这件案例中唯一可以作证的人。

verify v. (用事实)证实或核实。
I verified the store's address by calling to check it.               
我打电话询问，以核实商店的地址。