Abstract algebra is a field of mathematics that studies algebraic structures in an abstract way.

He used a syringe to inject the medicine.

He had to pay a fine for a parking violation.

The tough base of this mushroom is very hard.

He is the champion of the stone, paper, scissors game.

We need mutual understanding.

He believes in 'an apple a day keeps the doctor away', so he eats fruit every day.

Research on xenotransplantation has the potential to open new frontiers in medicine.

This river has a lot of small stones.

This rock is a type called nepheline.