the place something comes from or starts at, or the cause of something

a source of heat/energy/light 热源／能源／光源

a heat/energy/light source 热源／能源／光源

Oranges are a good source of vitamin C. 橙子富含维生素C。

Experts are trying to track down the source of the contamination in the water supply. 专家们正试图找到水源中污染物的来源。

We walked up the river to its source in the hills. 我们沿河上溯而行，一直走到其在山中的源头。

Money is often a source of tension and disagreements in young married couples. 金钱往往是年轻夫妇关系紧张不和的起因。

someone or something that supplies information

The journalist refused to reveal her sources (= say who had given the information to her). 记者拒绝透露消息的来源。

According to government sources (= people in the government) many MPs are worried about this issue. 政府方面透露，很多下议院议员对这个问题表示担忧。

According to congressional sources (= people who work in Congress) many Representatives are worried about this issue. 国会方面透露，很多众议员对这个问题表示担忧。

Always acknowledge your sources (= say which books you have used) at the end of a paper. 论文的末尾务必列出参考书目。

at the place where something comes from

Tax is deducted from my income at source. 我的工资还没拿到手就扣去了税金。

to get something from a particular place

Where possible the produce used in our restaurant is sourced locally. 我们餐厅尽可能用当地出产的农产品。