Englishfor English speakers
supplementary
Adjective
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If something is supplementary, it is added on; it is not needed, but it is often useful.
Many immigrants are employed but also feel the need to seek supplementary income.
These software solutions are more supplementary than basic.
contribution
Noun
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A contribution is something that you give or add.
Technology to reduce pollution could make a significant contribution to the solution.
Some of his most important early contributions were his detailed descriptions and illustrations.
Their contribution in October has been revised down from £300million to the same level.
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The money you give to someone, especially for a donation, is your contribution.
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The amount of work you did on a project.
His contribution was very low. He did almost nothing.