tropic /ˈtrɔpik/ n.［c］（常作sing.）回归线：the Tropic of Cancer(Capricorn) 北（南）回归线：The Tropic of Cancer is 231⁄2 degrees north of the equator and the Tropic of Capricornis 231⁄2 degrees south of the equator.北回归线是北纬231⁄2度，南回归线是南纬231⁄2度。 

tropical /ˈtrɔpikəl/ adj. 热带的：a tropical climate 热带气候；tropical crops 热带作物The hurricane was downgraded to a tropical storm when its speed dropped to 70mph. 飓风的速度降到每小时70英里的时候就变成了热带风暴。