The document discusses definite and indefinite articles ("a" vs "the") and provides examples of their usage. There are five sources that can make a noun definite: 1) if it is previously mentioned, 2) if it contains a superlative adjective, 3) if it is a unique entity, 4) if it contains a modifying phrase, and 5) if the context makes the identity clear. Count vs non-count nouns are also discussed, as well as examples of definite vs indefinite usage like "the milk" vs "a drop of milk". Photo credits are provided.