Army, n.
Etymology: [F. armée, fr. L. armata, fem. of armatus, p. p. of armare to arm. Cf. Armada.]
1. A collection or body of men armed for war, esp. one organized in companies, battalions, regiments, brigades, and divisions, under proper officers.
2. A body of persons organized for the advancement of a cause; as, the Blue Ribbon Army.
3. A great number; a vast multitude; a host. An army of good words. Shak. Standing army, a permanent army of professional soldiers, as distinguished from militia or volunteers.
Shades of meaning
An army is an organized body of men armed for war, ordinarily considerable in numbers, always independent in organization so far as not to be a constituent part of any other command. Organization, unity, and independence, rather than numbers are the essentials of an army. We speak of the invading army of Cortes or Pizarro, tho either body was contemptible in numbers from a modern military standpoint. We may have a little army, a large army, or a vast army. Host is used for any vast and orderly assemblage; as, the stars are called the heavenly host. Multitude expresses number without order or organization; a multitude of armed men is not an army, but a mob. Legion (from the Latin) and phalanx (from the Greek) are applied by a kind of poetic license to modern forces; the plural legions is preferred to the singular. Military is a general word for land-forces; the military may include all the armed soldiery of a nation, or the term may be applied to any small detached company, as at a fort, in distinction from civilians. Any organized body of men by whom the law or will of a people is executed is a force; the word is a usual term for the police of any locality.