That lone plane is flying in the sky.

He headed for the enemy's castle as a lone horseman.

He has a quick-tempered personality and gets angry quickly.

He has a short temper and gets angry quickly.

He learned the art of forging and made his own sword.

He forged a sword in the blacksmith.

He is interested in space exploration.

We are developing a robot to explore new planets.

He is focusing on a single problem.

In this experiment, we will use a simple substance called oxygen.