'Automobile' vs 'car': How are these two words different?

Solution 1:

The terms are roughly synonymous, but do have distinct uses that set them apart from each other as well. They both point to classes of vehicles, however the complete range of vehicles that would be encompassed be each term form distinct but overlapping sets.

Firstly car can refer to objects that aren't automobiles - railway carriages for example:

Full Definition of CAR

1 : a vehicle moving on wheels: as

• a archaic : carriage, chariot

• b : a vehicle designed to move on rails (as of a railroad)

• c : automobile

2 : the passenger compartment of an elevator

3 : the part of an airship or balloon that carries the passengers and cargo

source: Merriam-webster.com

Secondly automobile can be used as a general classifying term that is inclusive of vehicles other than cars (and not inclusive of non-wheeled, non-self-propelling instances of "car", such as airship gondolas etc.) as per:

source: http://what-when-how.com/automobile/general-classification-of-automobiles/