A figure of speech or rhetorical figure is a word or phrase that intentionally deviates from ordinary language use in order to produce a rhetorical effect. Figures of speech are traditionally classified into schemes, which vary the ordinary sequence of words, and tropes, where words carry a meaning other than what they ordinarily signify.
An example of a scheme is a polysyndeton: the repetition of a conjunction before every element in a list, whereas the conjunction typically would appear only before the last element, as in "Lions and tigers and bears, oh my!"—emphasizing the danger and number of animals more than the prosaic wording with only the second "and". An example of a trope is the metaphor, describing one thing as something that it clearly is not in order to lead the mind to compare them, in "All the world's a stage."
Rhetorical operations
Classical rhetoricians classified figures of speech into four categories or quadripita ratio:
addition (adiectio), also called repetition/expansion/superabundance
omission (detractio), also called subtraction/abridgement/lack
transposition (transmutatio), also called transferring
permutation (immutatio), also called switching/interchange/substitution/transmutation
These categories are often still used. The earliest known text listing them, though not explicitly as a system, is the Rhetorica ad Herennium, of unknown authorship, where they are called πλεονασμός (pleonasmos—addition), ἔνδεια (endeia—omission), μετάθεσις (metathesis—transposition) andἐναλλαγή (enallage—permutation). Quintillian then mentioned them in Institutio Oratoria. Philo of Alexandria also listed them as addition (πρόσθεσις—prosthesis), subtraction (ἀφαίρεσις—afairesis), transposition (μετάθεσις—metathesis), and transmutation (ἀλλοίωσις—alloiosis).
Figures of speech come in many varieties. The aim is to use the language inventively to accentuate the effect of what is being said. A few examples follow:
"Round and round the rugged rocks the ragged rascal ran" is an example of alliteration, where the consonant r is used repeatedly.