Poetic and rhetorical devices in Horace's poetry:

alliteration: repetition of sounds, generally first sound of a word.
Example: sensim sine sensu aetas senescit. (Cicero, de Senectute, 11.28)

anaphora: repetition of words, or closely related words, to introduce successive clauses or lines, for emphasis.
Example: Epode 2 (Chapter 41): "neque excitatur ... neque horret. . . ."

apostrophe: direct address to someone who is not present, or to a mythical or historical figure.
Example: Serm. 1.9 (Chapter 45): "o te Bolane cerebri felicem!"

assonance: repetition of vowel sounds in the middle of a line.
Example: Ep. 2 (Chapter 41): futurus rusticus

chiasmus: abba word order.
Example: Ode 2.7 (Chapter 42): "dis patriis Italoque caelo". In these two noun-adjective groups, the first is noun-adjective order, while the second is adjective-noun order.

hendiadys: "one for two"; use of two grammatically parallel words to describe what is really one idea.
Example: Odes 3.7 (Chapter 42): "Philippos et celerem fugam"; Philippi and swift flight aren't two separate things Quintus experienced but one thing, flight from Philippi or flight at Philippi.

irony: a meaning that turns out to be the opposite of what it seems.
Example: Epode 2 (Chapter 41): the first part of the poem, a heart-felt praise of rural life, turns out to be spoken by the money-lender Alfius, who either never had any intention of moving to the country, or else can't extricate himself from the rhythm of the money-lending cycle of the city.

metaphor: comparison without the use of like or as.
Example: Serm. 1.9 (Chapter 45): "demitto auriculas" (as if he is the donkey).

metonymy: use of a word for something else.
Example: Epode 2 (Chapter 41), "superba limina": what the "beatus" avoids isn't just the physical house, or physical threshold, but the entire client-patron relationship, which is humiliating to the client who has to wait at the beck and call of the wealthy and powerful.

onomatopoeia: use of a word which sounds like what it means.
Example: Epode 2 (Chapter 41), "mugientium": the first syllable, "mu-", recalls the mooing sound of cattle.

personification: attribution of human qualities to inanimate objects.
Example: Serm. 1.5 (Chapter 44): "nox inducere terris /umbras . . . parabat", as if nox could prepare, implying intend, an action.

simile: comparison using like or as.
Example: Serm. 1.9 (Chapter 45): "ut iniquae mentis asellus", where Horace explicitly compares his attitude to that of a bad-tempered donkey.

synchysis: interlocked word order (abab), in which the "a" words and the "b" words are linked, with an interlocking effect.
Example: Epode 2 (Chapter 41): "pressa puris mella amphoris". "pressa . . . mella" are intertwined with "puris . . . amphoris".

synecdoche: the part for the whole.
Example: Odes 2.7 (Chapter 43): "caelo" for all of Italy; "latus" for the whole body.