不可数。做名词时的意思：果酱；拥挤；堵塞；卡住（因而发生故障）。做动词时的意思：使劲（往某处）挤（或压、塞）；（使）卡住，不能动弹，不能运转；塞入；塞进；挤进。
Jam例句
1、Pass me thejamplease.
2、Car and Motorcyclejamin Taipei.
3、Maybe he in the trafficjam.
4、His fingers are sticky withjam.
5、This kind ofjamis made of berry.
6、They detoured around the trafficjamby heading south.
7、The trafficjamhappened at a highway junction.
8、The root-ginger should be crushed up before it is added to the boilingjam.
9、Delicious with butter, raspberryjamor filled with scrambled eggs for any meal.
10、The bigger display attracted more customers but very few of them actually boughtjam.