The document discusses diagramming sentences where the subject is modified by an adjective. It states that the subject of a sentence can be modified by one or more adjectives, as adjectives answer questions like "which", "what kind", "how many", and "whose". When diagramming a sentence, any adjectives modifying the subject are written on lines below the subject term. Examples are provided where the subject "girl" is modified by "bashful young" and the subject "Bible" is modified by "old family".