An imaginary unit is an important concept in mathematics.

An astronomical unit represents the average distance from the Earth to the Sun.

This product has a very small assembly unit.

The International Workers' Association is historically an important organization.

He is an expert in systems engineering.

Our school has introduced a new PA system.

The filesystem of my computer has broken down.

He has a very passive personality.

I am very interested in social science.

The standard language of Japan is based on the Tokyo dialect.