[ pen-tad ]
/ ˈpɛn tæd /


a period of five years.
a group of five.
the number five.
Chemistry. a pentavalent element or group.
Climatology. a period of five consecutive days.

Origin of pentad

1645–55; < Greek pentad- (stem of pentás) group of five. See pent(a)-, -ad1 Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

Examples from the Web for pentad

British Dictionary definitions for pentad


/ (ˈpɛntæd) /


a group or series of five
the number or sum of five
a period of five years
chem a pentavalent element, atom, or radical
meteorol a period of five days

Word Origin for pentad

C17: from Greek pentas group of five
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012