Solving a quadratic equation is difficult.

Reijiro is my best friend.

Redistribution of this software is prohibited.

In Japanese grammar, postpositions play an important role.

A back vowel is a sound where the back of the tongue approaches the palate.

Back vowels are vowels that are pronounced using the back of the tongue.

Postfix notation is one method of expressing calculations.

The Kokin Wakashū is the second collection of the Chokusen Wakashū.

Tokudaiji Sanesada, also known as Goto Tokudaiji Sadaijin, was a court noble and a literary person during the Heian period.

He is doing special exercises to strengthen his tibialis posterior muscle.