Other forms: compendia, compendiums
A compendium is a concise collection of a whole body of knowledge. A compendium of games, a useful compendium, compendium of law.
The concision is the promise: a compendium gathers a subject into one manageable volume, which is why the word appears on reference books and on boxes of assorted board games. The plural is compendia or compendiums. Note that the Latin means a saving or a shortcut, from weighing together.
1nouncompendiumA concise collection of a whole body of knowledge.
“The book is a compendium of everything known about medicinal plants.”
compendium is a collection.
Latin compendium means a saving or shortcut, from com plus pendere, to weigh. Pension and compensate come from the same weighing.
Proto-Indo-European
*(s)pend-
Latin
compendium — that which is weighed together; a sparing, a saving, an abbreviation
English, today
compendium
Built from
From the Latin compendium (“that which is weighed together; a sparing, a saving, an abbreviation”), from con- (“with”) + pendō (“to weigh”).
Etymology from Wiktionary, CC BY-SA