Any selection extracted from a larger text for special consideration. Classically the term was used in synagogue & church liturgies to designate a selection from a biblical text assigned for public reading.  Modern biblical scholars generally use the term to refer to the small self-contained units from which a book was originally composed. A pericope may be as short as a single line aphorism or proverb or as long as the Sermon on the Mount (111 verses) or the Passion Narrative (127 verses in Luke). But the term is most often used to designate moderate sized segments of logically related sayings and/or narrative material:

• a parable (like the Sower),
• clusters of aphorisms (like the Lamp & the Measure),
• a pronouncement story (like Jesus' True Kin),
• a miracle story (like the feeding of the 5000),
• a narrative scene (like the Crucifixion).

Other On-line Resources:

• Pericope - brief article defining term and use (Wikipedia)
• Pericope: Scripture as written and read in antiquity - website of literary scholars researching the composition and use of paragraphing in ancient literature (posted by The Pericope Group).