Originally posted by penndragonn Lot of letters describing these lenses. Need a guide!
It's not that bad once you figure it out.
SMc and HD : coatings. Both are fine, HD is more recent.
SDM and DC : AF system. DC is more recent, faster and more reliable. Both are silent. They supersede the screwdrive that was used in older lenses (which is noisier, but very reliable. Screwdrive does not work well in live view).
For the rest, I recommend reading one of the recent lens reviews, where such acronyms are generally explained in the specifications page.