Number & MeasureGreek → English
Pentad
/ˈpɛntæd/noun
A set of five things, and in climatology a fixed five-day period.
The Greek roots
πεντάς
pentás
group of five
Literally: “a group of five”
Follow a root:πεντάς1 word
The story of the word
Pythagorean arithmetic treated such groups as objects in their own right, so a pentad was a set of five rather than the numeral 5. Climatology found a use for that: five-day pentads divide a 365-day year into exactly 73 blocks, which is why so many long weather series are tabulated in pentads. πέντε runs through pentagon, Pentecost, the fiftieth day, and the Pentateuch, the five scrolls of Moses, where τεῦχος started as a tool or vessel, became the case a scroll was kept in, and ended up meaning the book itself.
- How it travelled
- Ancient Greek → Late Latin → English
- First recorded
- 17th century
Same family
pentagonPentecostPentateuchpentathlon
In a sentence
Rainfall is averaged over pentads to smooth out single storms.
He grouped the reforms into a pentad and gave each one a colour.