Although technically anything that light can shine through is translucent, most writers now reserve this word for substances that don’t clearly display what is on the other side. A frosted window-pane, a thin rice-paper screen, or a sheet of tissue paper may be called “translucent.” A clear window or camera lens is transparent. “Sheer” fabric can be either translucent or transparent. Better check before you go out in public.
“Opaque” is the opposite of “translucent.” Anything solid through which light cannot pass is opaque.