Semi Means Half, but Semi-Annual Is Ambiguous
Semi means half. In practice the prefix causes more confusion than it resolves.
Semi means half, and stands alone for a semi-detached house, a semi-final or an articulated lorry. The prefix is a reliable source of ambiguity: *biannual* and *semi-annual* are supposed to mean twice a year while *biennial* means every two years, but the first pair is so widely confused that careful writers avoid both and say *twice a year*. *Bimonthly* and *biweekly* are worse, having no agreed meaning at all. Latin *semi* is related to Greek *hemi*, as in *hemisphere*, and to English *half* by a distant root.
- Half. *Semi-circle.*
- A semi-final. *The semis.*
- A semi-detached house. *A semi.*
- A lorry (US). *A semi.*
- Latin — *semi*, half. *The root.*
Word forms
| Form | Word | Example |
|---|---|---|
| Prefix | semi- | Semicircle. |
| Noun | semi | A semi. |
| Greek | hemi- | Hemisphere. |
| Related | demi- | Demitasse. |
| Latin | semi | Half. |
- They reached the semis.Sport.
- A semi-detached house.Housing.
- Semi means half.Etymology.
Three ways to say half
- Semi- — Latin: semicircle, semi-final, semiconductor
- Hemi- — Greek: hemisphere, hemiplegia
- Demi- — French: demigod, demitasse, demisemiquaver
- A demisemiquaver uses two of them at once
- Half itself is the native Germanic word
Latin *semi*, half, related to Greek *hemi* and distantly to English *half*.
Does semi-annual mean twice a year?
It is supposed to, but the pairing with biannual is so widely confused that twice a year is the clearer phrasing.
What is the difference between semi, hemi and demi?
All mean half, from Latin, Greek and French respectively. A demisemiquaver combines two of them.