Does Heavy Armor reduce your speed?

I noticed in the PHB, page 20, under Speed for Dwarves:

Speed. Your base walking speed is 25 feet. Your speed is not reduced by wearing heavy armor.

However, I cannot find anywhere in PHB that mentions that wearing Heavy Armor imposes any speed reduction.

Does anyone know if I’ve missed something, or if this is actually some inconsistency in the book and Heavy Armor in fact doesn’t impose any speed reduction?