Fujitsuko is my best friend.

I was disappointed by his insincere attitude.

This system is too irrational to understand.

I am surprised at the irrationality of this system.

This compound is an unsaturated hydrocarbon.

This chemical reaction is irreversible.

His unwavering determination became the power to overcome all difficulties.

Invisible light rays are not visible to the human eye.

There is an inconsistency between his story and the facts.

He made an indiscreet remark and troubled those around him.