Decad

Part of speech: noun

Definitions

1. A series or group that consists of ten units ; a division of written works or collections into sets of ten ; any period or phase that spans ten parts or years
2. A unit, sequence, or organizational grouping totaling ten items ; the subdivision of literature or other items into decuples ; a term for any duration or enumeration involving ten elements
3. Any organizational structure, period, or listing composed of ten entities ; a way of arranging or classifying in sets of ten ; a specific term for ten-year intervals or ten-part divisions

Etymology: "Decad" is a doublet of "decade", the two forms descending from the same Greek and Latin roots but reaching English by different routes. The Greek "dekas" meant a group of ten, and it gave rise to "dekad" as a term for a set of ten things, while "decade" arrived through a related Latin-based channel. English kept both, so the word now sits alongside its near twin with a narrower reach. The element "dec-" comes from the Greek "deka," meaning ten, the same number root that appears in "decimal," "decathlon," and "December," originally the tenth month of the early Roman calendar. The ending "-ad" is a Greek-derived suffix used to form nouns denoting a unit or group, so "decad" is built from the number ten plus a group-forming ending.

Synonyms: decade, ten years