Englishfor English speakers
persistent
Adjective
—
If someone or something is persistent, they continue and do not give up quickly.
She has had a persistent cough for weeks.
There was a persistent knocking on the door.
Many youth who spend time in jail actually become persistent offenders.
There have been persistent rumors for years.
—
ing past maturity without falling off.
Pine cones have persistent scales.
chemical
Noun
—
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
—
Of or about chemicals.
This test can detect small changes in the chemical composition of water.