An appeal made by a poet to a muse or deity for help in composing the poem. The invocation of a muse was a convention in ancient Greek and Latin poetry, especially in the epic; it was followed later by many poets of the Renaissance and neoclassical periods. Usually it is placed at the beginning of the poem, but may also appear in later positions, such as at the start of a new canto. The invocation is one of the conventions ridiculed in mock-epic poems: Byron begins the third Canto (1821) of Don Juan with the exclamation ‘Hail, Muse! et cetera’. In terms of rhetoric, the invocation is a special variety of apostrophe.