English has numerous prefixes that signify “half. “Why do we need so many? And what’s the difference?
1. Prefix Semi- in English
The earliest and most common prefix in English is semi-, which comes from Latin and means “half”. Semi- was first employed in the direct sense of “half” in the word ‘semicircular’, but it quickly became connected with notions that are harder to measure.
A semi-circle is easy to recognize, but what does it have to look like to be considered ‘semi-abstract’? And what exactly is meant by ‘semi-permanent’? Through more abstract usage that grew prevalent in the 1800s, the prefix semi- also developed to imply “almost” or “somewhat,” as in “semiamusing” or “semi- semi-angry” (slightly displeased).
2. Prefix Hemi- in English
In Greek, hemi- means “half. ” It is less common than semi- and is more associated with technical language in fields such as chemistry, biology, and anatomy. The “half” meaning implies symmetry along the vertical axis.
For example, a hemicylinder is not a half cylinder in the sense of upper half, lower half; rather, it is a half sliced lengthwise. Similarly, hemiplegic refers to paralysis of the left or right side, whereas paraplegic refers to paralysis of the lower half. The term “hemisphere” is a specific instance because a sphere is symmetrical on all sides.
3. Prefix Demi- in English
Demi means “half” in French. It was initially used in English to discuss heraldry, where terms such as demi-angels (half-man, half-angel), demi-lions (half-man, half-lion), and demi-horses (half-man, half-horse) emerge. It also appears frequently in various sectors, such as military (demi-brigade: semi-brigade) and fashion (demi-cap, demi-lustre, demi-worsted). It also implies “virtual” or “less than”. For example, a demigod is not a legitimate deity, and a demicannon is a medium-sized cannon.
It appears ludicrous that English should borrow the prefix “half” from three different languages, but otherwise we wouldn’t have a word like ‘hemidemisemiquaver’ for ’64th note’, instead of having to say ‘the 2nd-2nd-2nd-2nd-8th note’.