cracker：
firework consisting of a small explosive charge and fuse in a heavy paper casing
同义词：firecracker
例句：
The boys light crackers in the street.
男孩们在街道上放鞭炮。
firecracker
firework consisting of a small explosive charge and fuse in a heavy paper casing
同义词：cracker
例句
Chinese children like to buy many firecrackers before the Spring Festival.
中国孩子会在春节前买很多鞭炮
firework
(usually plural) a device with an explosive that burns at a low rate and with colored flames; can be used to illuminate areas or send signals etc.
例句
The climax of the celebration was a firework display.
庆祝会的高潮是燃放烟火。
所以，cracker和firecracker是对等同义词。
但是firework是范围更大的词汇。
