Linked from
The 8 pages that link to Tropics, each with the reason it gives.
SolsticeNarrower topic: The solstice declinations set the latitudes of both tropics.
Tropic of CancerNarrower topic: This latitude marks the tropics’ northern boundary.
ZingiberaceaeRelated: Most ginger-family diversity occurs in tropical regions, especially in Asia.
Tropical AmericasNarrower topic: The region takes its name from this latitude-defined belt.
Hemispheres of EarthRelated: The region crosses both Northern and Southern Hemispheres.
ImpatiensRelated: Most Impatiens species occur in tropical and subtropical regions.