There are electronic thesauri, but check out the original to enjoy a stupendous accomplishment. A thesaurus can also be a set of terms used for indexing or classification or a list of keywords. A hard drive that is only about one inch tall - a perfect fit for laptops. A graphics format used for saving or creating high resolution bit maps and gray scale images. TIFFs were invented for scans.
Halftones only apply to gray or color areas.
A halftone breaks a gray area into dots that a printer can print. If there is no special effect halftone that you need, don't bother saving it as a halftone - let the PostScript printer halftone it for you on the way out. Yes, all PostScript printers can take any gray or color and break it into lines per inch. This is how many diacritical marks and accents are typed on the Mac. The space at the top of a window containing the name of the window, a close box and usually a zoom box.