a drop in the bucket 杯水车薪

“杯水车薪”，汉语成语，意思是用一杯水去救一车着了火的柴草（trying to put out a blazing cartload of faggots with a cup of water），比喻力量太小，解决不了问题。与英文习语“a drop in the bucket”意思相近。

例句：

这些捐款只是杯水车薪。
These contributions are just a drop in the bucket.

许多公司捐赠食品和药品来帮助地震幸存者，但与所需物资相比这只是杯水车薪。
Many companies donated food and medicine to help the survivors of the earthquake, but it was just a drop in the ocean of what was needed.