vade mecum \vay-dee-MEE-kuhm; vah-dee-MAY-\, noun:
1. A book for ready reference; a manual; a handbook.
2. A useful thing that one regularly carries about.
The reader who wants honestly to understand it, and not merely read
into it his own ideas, needs some kind of vade mecum to provide
the necessary background and explain unfamiliar words and allusions and strange
turns of thought.-- Robert C. Dentan, "Including Uz and Buz", New York Times, November 17, 1968
Roget's Thesaurus, which had come into being as a linguistic example of the
Platonic ideal, became instead a vade mecum for the crossword
cheat.-- Simon Winchester, "Word Imperfect", The Atlantic, May 2001
Vade mecum is from Latin, literally meaning "go with
Question for my readers:
What is your vade mecum?
Mine? depends on the day:
Taber's medical encyclopedia or Focus Guide to North American Birds