Doublet is an important concept in linguistics.

A diphthong refers to the phenomenon where two vowels are pronounced consecutively within a single syllable.

This house is warm even in winter because it has double-pane windows.

He is from the United States of America.

I live in Japan.

I love Japan.

Ancient Japan was a place where beautiful nature and culture merged.

His ship entered the port, flying its jack.

He has multiple citizenships and holds passports from America and Japan.

He was left in a state of statelessness, belonging to no country.