compendium (n.)

"brief compilation containing the general principles or leading points of a longer system or work," 1580s, from a Medieval Latin use of Latin compendium "a shortening, saving," literally "that which is weighed together," from compendere "to weigh together," from com "with, together" (see com-) + pendere "to hang, cause to hang; weigh; pay" (from PIE root *(s)pen- "to draw, stretch, spin"). Nativized earlier in English as compendi (mid-15c.).