contaminant

"The factory's waste contaminates the nearby river, making the water unsafe to drink. "

"The scientist carefully examined the strange matter in the lab. "

"The foreign student in my class has a different cultural background than the rest of us. "

"My sister brought several books to the library, and that one is about dinosaurs. "

"The farmer had a put on the tomatoes, guaranteeing a price of $2 per pound. "

"Even animals in the Jewish system cause impurity only when they are dead."

"The castle's keep stood tall above the surrounding walls. "

"It looks weaker and weaker, the more I think about it."

"The doctor carefully examined the child's swollen lid. "

"My grandmother keeps her favorite olive oil in a large, old clay jar. "

"By now, you must surely know which is which."

"Put the lid on the jar to keep contaminants out."