Hendiatris (Greek for one through three) is a figure of speech used for emphasis, in which three words are used to express one idea.
For example, the German phrase "Wein, Weib und Gesang" (wine, women and song), or the modern English equivalent "Sex and Drugs and Rock and Roll", use three words (counting "rock and roll" as one) to capture one idea (which may be "to party", or to adopt a certain lifestyle).
If the units involved are not single words, and if they are not in any way synonyms but rather "circumnavigate" the one idea expressed, the figure may be more correctly, precisely, and expediently described as a triad.
See also