B2the place something comes from or starts at, or the cause of something: a source of heat/energy/lighta heat/energy/light sourceOranges are a good source of vitamin C.Experts are trying to track down the source of the contamination in the water supply.We walked up the river to its source in the hills.Money is often a source of tension and disagreements in young married couples.Origins and sourcesC1someone or something that supplies information: The journalist refused to reveal her sources (= say who had given the information to her).According to government sources (= people in the government) many MPs are worried about this issue.Always acknowledge your sources (= say which books you have used) at the end of an essay.People who reveal secrets and tell talesat source›at the place where something comes from: Tax is deducted from my income at source.TaxationOrigins and sources