the central part of a car wheel (or fan or propeller etc) through which the shaft or axle passes
"The mechanic tightened the bolt on the hub to ensure the new tire would spin smoothly without wobbling."
a center of activity or interest or commerce or transportation; a focal point around which events revolve
"the playground is the hub of parental supervision"
"the airport is the economic hub of the area"
The central part, usually cylindrical, of a wheel; the nave.
"The mechanic tightened the lug nuts onto the hub to ensure the wheel stayed securely attached while driving on the rough road."
In plain English: A hub is a central place where many things connect or meet together.
"The city serves as the main transportation hub for the entire country."
Usage: A hub refers to the central part of a wheel where spokes are attached and the axle fits. In common usage, it also describes any central point or place where things connect, such as a transportation hub.
Hub comes from an earlier dialectal form of hob, though its ultimate origin remains unknown. The word likely relates to German words meaning "bump" or "hill," suggesting it originally referred to a raised spot on a surface before taking on its current mechanical sense.