The problem of illiteracy is a serious social issue around the world.

His behavior is illogical and incomprehensible.

His behavior was illogical and I couldn't understand it.

This problem requires solving a nonlinear equation.

He always proactively suggests new ideas.

This document is written in the standard print font.

He was criticized for having a double standard.

The song of Naniwa-zu is one of the ancient Japanese poems.

My favorite song is Aegukka.

I heard the beautiful song of a common blackbird in the park.