tropic phoneticPhoneticPhoneticPhoneticPhoneticPhoneticPhoneticPhoneticPhoneticPhoneticPhonetic PhoneticPhoneticPhoneticPhoneticPhoneticPhoneticPhoneticPhoneticPhoneticPhoneticphonetic noun [C] 
one of the two imaginary lines around the Earth at approximately 23.5 degrees north and 23.5 degrees south of the Equator 

The Tropic of Cancer is the northern tropic, and the Tropic of Capricorn is the southern one. 

tropics phoneticPhoneticPhoneticPhoneticPhoneticPhoneticPhoneticPhoneticPhoneticPhoneticPhoneticPhonetic PhoneticPhoneticPhoneticPhoneticPhoneticPhoneticPhoneticPhoneticPhoneticPhoneticPhoneticphonetic plural noun 
The tropics is the hottest area of the Earth, between the Tropic of Cancer and the Tropic of Capricorn. 
She's a botanist and spent several years researching in the tropics.
The toucan is a largish brightly-coloured bird with an enormous bill which is native to the New World tropics.

tropical phoneticPhoneticPhoneticPhoneticPhoneticPhoneticPhoneticPhoneticPhoneticPhoneticPhoneticPhoneticPhoneticPhonetic PhoneticPhoneticPhoneticPhoneticPhoneticPhoneticPhoneticPhoneticPhoneticPhoneticphonetic adjective [not gradable] 
Something that is tropical is from or relates to the area between the two tropics. 
Leprosy is one of the few tropical diseases which could be eradicated early in the 21st century.
She's decided to specialise in tropical medicine (=the treatment of diseases from the tropical areas of the world).
I'd love to live somewhere with a tropical climate.
The organization has campaigned vigorously against imports of tropical hardwoods.
Tropical forests contain around half of all the world's species of animals and plants.
The Amazon river basin contains the world's largest tropical rainforest .
The hurricane was downgraded to a tropical storm when its speed dropped to 70mph.
FIGURATIVE The weather was tropical (=extremely hot) last summer.
See also subtropical.
( Cambridge International Dictionary of English )