Mobility means different things to different people. Some people are quite happy being able to get around town. Others view the world in terms of time distance-four hours from Chicago to San Francisco by airline, perhaps. Obviously, range of motion is an important aspect of mobility.
Another factor in mobility is ease of access. What might be considered mobile in one context is quite immobile in another. Certainly the pioneers crossing the North American continent in ox-drawn wagons covered the same distance as the airliner from Chicago to San Francisco. But we would today hardly consider these pioneers to have had much mobility.
A more pertinent example of mobility is the ever decreasing size of cellular telephones. What was once considered a "mobile phone" had to be transported in a vehicle. A major step forward was the "transportable" phone, which freed the user from their vehicle but weighed in at about twenty pounds, still huge by today's standards. With the advent of "brick" phones in the mid-1980's came the era of "portable" phones. This continuing decrease in size and weight of handsets has greatly increased the mobility of cellular subscribers.
In this book on mobile data communications we define mobility asthe ability to send and receive communications anytime anywhere. Mobility means that both source and destination devices, applications and people are free of the constraints imposed by physical location. Access to an Ethernet port, for example, need not limit one's ability to send and receive data in a mobile WAN environment any more than access to a landline phone currently limits one's ability to place a voice call in an area covered by cellular service.