exposition

Concise Oxford English Dictionary © 2008 Oxford University Press:
exposition/ekspəˈzɪʃn/

▶noun

• 1 a comprehensive description and explanation of a theory.

• 2 a large public exhibition of art or trade goods.

• 3 Music the part of a movement, especially in sonata form, in which the principal themes are first presented.

• 4 archaic public exposure.

– derivatives
expositional adjective.

– origin ME: from L. expositio(n-), from exponere (see expound).