Figures - history
There has been much study of Figures of speech through the ages. It began with the first students of language of whom we have records - at least in European languages. These were the Greeks, followed by the Romans, who in this case as so many others gave a lead to the whole western academic tradition.
As more and more scholars gave more and more time to the subject, so they became ever more precise and detailed in their distinctions. The number recognised increased as a result. The anonymous Rhetorica ad C. Herennium (in Latin) of around 85 BCE only listed 65 different figures. By 1577 Peacham's Garden of Eloquence (in English) listed nearly 200. Richard A. Lanham published A Handlist of Rhetorical Terms in 1969 in the USA which lists figures of speech in 105 pages, with over ten such terms per page - giving a total of more than 1,000 different figures of speech. (Lanham's book - which I find absorbing - shows the 'advances' that modern scholarship has made.) While there is some value to advanced scholars in being able to distinguish between the minute differences between different figures, ordinary users of the English language are unlikely to need all the terms even in this guide. See for example Syllepsis - zeugma.
Much of the discussion turned on how to classify the different figures of speech. Much of this discussion is sterile; some seems wrong-headed to me; some just wrong. Certainly you will find some very different, and even contradictory, advice and definitions if you look through the historical sources.
(There is a useful "guide to the terms of classical and renaissance rhetoric" called "The Forest of Rhetoric [or] silva rhetoricae" [the Latin name) by Dr. Gideon Burton of Brigham Young University at [] (available in May 2008). Dr Burton says "Sometimes it is difficult to see the forest (the big picture) of rhetoric because of the trees (the hundreds of Greek and Latin terms naming figures of speech, etc.) within rhetoric.")