As I understand it, both the prefixes "Hept-" and "Sept-" are used to indicate seven of something.
We have examples of English words that use both:
e.g.
Heptathalon, Heptagon, Heptane
vs
Septuagenarian, September
I don't believe this is the case for other numbers- "Quad" is four, "Pent" is five, "Hex" is six, etc…
I believe "Sept" comes from the word "septem", which is Latin for "seven". So where has "Hept" come from? And why do no other numbers have an equivalent?
Best Answer
It's the difference between Latin and Greek. Four, five and six do have their own forms.
Latin: bi-, tri-, quad-, quin-, sex-, sept-...
Greek: di-, tri-, tetra-, pent-, hex-, hept-...
Generally, Latin prefixes are added to Latin roots and Greek prefixes to Greek roots.
Quadrilateral, quintuplet, September etc.;
Tetrahedron, heptagon etc.