"北回帰線" は英語で 'tropic of cancer' といいます。
"南回帰線" は英語で 'tropic of capricorn' といいます。
説明するときは、写真を見せた方がいいと思います。
The Tropic of Cancer is an imaginary line that crosses the most northern part of the Earth where the sun can appear directly overhead. Countries such as Egypt, Saudi Arabia, Myanmar, Taiwan, and Mexico fall underneath it. The Tropic of Capricorn is the most southern part of the Earth where the sun can appear directly overhead. Countries such as Argentina, South Africa, Madagascar, and Australia fall underneath it.
アメリカ合衆国 
