回归线的英文：
tropic

Between or within the tropics.
南北回归线之间的热带地区之间或之内的

Termites are principally tropical in distribution.
白蚁主要分布在热带地区。

Dry rosin is best in tropic.
干的松香在热带最适用。

The flora that originated from tropical is a transition from tropic to temperate.
植物区系具有热带起源性，是从热带向温带过渡的阶段。

Many sub-tropical and tropical fruits can withstand this treatment.
许多亚热带和热带水果能经受这种处理。

large order of chiefly tropical liverworts.
主要为热带地钱的一个大目。