Translation guide
In Japanese, the word for 'archipelago' is most commonly 諸島 (shotō), used as a suffix to name specific island groups. The standalone term 群島 (guntō) also exists but is less common. Japan itself is an archipelago, and the term 日本列島 (Nihon Rettō) refers to the Japanese archipelago.
archipelago
Most common general term; often used as a suffix.
The learner wants to refer to an archipelago in general, or to name a specific archipelago.
Japan is made up of many archipelagos.
The Philippine archipelago is known for its beautiful beaches.
Also means 'archipelago' or 'island group'. Slightly more technical or geographical than 諸島, and often used in proper names like 南西諸島 (Nansei Shotō) vs. 南西群島 (less common). In many contexts, 諸島 is preferred.
Rare flora and fauna inhabit this archipelago.
Means 'chain of islands' or 'archipelago', emphasizing a linear arrangement. Most famously used in 日本列島 (Japanese archipelago). Not used as a general standalone term for any archipelago.
The Japanese archipelago stretches long from north to south.
The learner wants to talk about Japan as an archipelago.
諸島 (shotō) is the most common and versatile word for 'archipelago'. 群島 (guntō) is more technical and often appears in official geographical names. 列島 (rettō) specifically refers to a chain of islands and is rarely used alone; it's almost always part of a proper name like 日本列島.
To name a specific archipelago, attach 諸島 to the place name: ハワイ諸島 (Hawaiian archipelago), インドネシア諸島 (Indonesian archipelago). For Japan, 日本列島 is the idiomatic choice.
The Japanese archipelago is located on the Pacific Ring of Fire.