Most of those definitions can be reduced to a single definition: "the" <something> = the speaker believes that enough information has been given for the listen

Most of those definitions can be reduced to a single definition: "the" <something> = the speaker believes that enough information has been given for the listener to know which <something> is being referred to. Examples: "the man who hit me" - makes sense as part of a story where only man hit me. "the world" - there is only one world, so we know which one it is.