迪 is a bound morpheme (b.f.) that cannot stand alone as a word. In modern Chinese it appears almost exclusively in two contexts: (1) as the first character in transliterations of foreign names and loanwords like 迪斯科 (disco, from 'disco'), 迪拜 (Dubai), and 迪士尼 (Disney); and (2) as the second character in the literary compound 启迪 ('to enlighten', 'to inspire'). You should never use 迪 by itself — always pair it with the other syllable(s) of the compound.