1 [C] (plural media or mediums) a means you can use to express or communicate sth （表达或沟通的）媒介，方法，手段: English is the medium of instruction in the school. 英语是这所学校的教学语言。 ☞Look at media and mass media. 参看media及mass media。

2 [C,U] medium size 中等尺寸；中号: Have you got this shirt in (a) medium? 这件衬衫有中号的吗？

3 [C] (plural mediums) a person who says that he/she can speak to the spirits of dead people 灵媒；通灵的人

4 (in biology) a substance that sth exists or grows in or that it travels through （生物学）培养基，生长或活动环境: Good clean garden soil is the best sowing medium. 优良干净的花园土壤是最佳的播种环境。