dyna-
In the derivatives of Gr. δύνα-σθαι to be able, δύναµις power, y (= Gr. υ) is etymologically short, and is so treated in pronouncing dictionaries down to the middle of the 19th c. But popular usage (esp. since dynamite came into vogue) tends to give the y the diphthongal pronunciation (aɪ) in all these words, though (dɪn-) is still preferred by some in dynamic and its family, and app. by most scholars in dynasty and its family.