- 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
Examples from the Web for pentad
But this oddness belongs to other numbers also (pentad, heptad, &c.).Aristotle
In 1820, he added to the last a pentad, so that the whole list amounted to sixty-five.Man and His Migrations
R. G. (Robert Gordon) Latham
Five, or the pentad, is everything; it stops the power of poisons, and is dreaded by evil spirits.Three Thousand Years of Mental Healing
George Barton Cutten
Nitrogen in the triad condition in the amines is far less poisonous than in the pentad condition.Poisons: Their Effects and Detection
Alexander Wynter Blyth
There is something to be said for this view, but on the whole the balance of the evidence is in favor of nitrogen being a pentad.
- 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 and History for pentad
1650s, from Greek pentas (genitive pentados) "group of five" (see five). Meaning "period of five years" is from 1880; meaning "period of five days" is from 1906, originally in meteorology.