1. A large body of people organized and trained for land warfare.
2. A tactical and administrative military unit consisting of a headquarters, two or more corps, and auxiliary forces.
3. Where Marines are trained to use Armor, the Air Force and Navy received their start in aviation, and the professional soldiers that not only take and control tactical positions on the modern battlefield, but maintain these positions under severe and adverse conditions.
Often mocked by Marines (bullet sponges), Navy (squids), and Airforce (too many silly names to list). Rivalry is encouraged among the different branches of the military, as a way to buid "espres de corp".
As a side note, the Army trains the only Cavalry Units in the modern US Military, and as any Scout will tell you: "If you ain't CAV, you ain't SHIT".
I joined the Army to learn valuable skills in anticipation of putting myself through college with the Montgomery GI Bill. That's why I learned to drive Bradleys, fire crew-served weapons, call for Arty, and use C4 on bridges.
What the hell was I thinking? Only Cops in LA need those skills.