DOD is the written short form of the US Department of Defense — the part of the American government that runs the army, navy, air force, and related offices. You see DOD in news, on official papers, and in job titles. People say the three letters D-O-D; they do not say it as one word. The American spelling is Defense, not the British Defence, which is why that D is that D. In Taiwan, news readers will often just say 美國國防部, and still print DOD beside it. The Pentagon is the famous building, not the same word, though writers sometimes treat them as twins. This abbreviation, in this filing, is only that US department. Other fields use DOD for other things; that is a different file.