Linked from
The 79 pages that link to Friction, each with the reason it gives.
LubricationNarrower topic: Lubrication reduces this resistance at interacting surfaces.
TractionNarrower topic: Traction is the useful grip produced by friction at a contact interface.
Disc brakeNarrower topic: Friction at the pad–rotor interface converts rotational energy into heat.
Bicycle brakeNarrower topic: Friction at the pad and braking surface slows wheel rotation.