Englishfor English speakers
chemical
Noun
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A chemical is a basic substance that is used in or produced by mixing elements or other chemicals.
When you burn plastics, you put dangerous chemicals into the air.
The chemical industry in China is producing more and more useful paints, glues, and other products.
chemical
Adjective
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Of or about chemicals.
This test can detect small changes in the chemical composition of water.
barrier
Noun
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A barrier is something that stops passage; it does not allow anything to get through it.
The barrier across the road stopped traffic from getting past it.
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A barrier is an obstacle; it is something to prevents progress.
The bug in the code was a barrier to us completing the project on time.
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A barrier is a boundary or limit.
The wall surrounding the jail was a barrier to all those who want to get out.