前缀hemi-意思是“半”，这个前缀与另二个前缀虽然，意思都表示“半”但是，前缀hemi-来源于希腊，而另二个semi-和demi-来源于拉丁语。前缀hemi-多见于外来词及科学术语，它的引申义是“其次”的意思。以下是关于这个前缀的英文词源介绍。

word-forming element meaning "half," from Greek hemi- "half," from PIE root *semi-, which is the source of Sanskrit sami, Latin semi- (see semi-), Old High German sami- "half," and Old English sam-,denoting a partial or imperfect condition (see sandblind).
——————《英语词源在线字典》

hemi-,pref.in words of Greek origin,meaning 'half.—Gk.,for *sēmi-,cogn.with OI.sēmí,'half,L.sēmi-,OE.sām-,OHG.sāmi-,'half. See semi-.
——————《克莱因英语词源字典》

词例：

1.hemisphere [hemi- 半 + sphere 球]
n. 半球

2.hemiplegia [hemi-半 + plegia n. [医]麻痹，瘫，瘫痪 → “身体一半瘫痪了” →]
n.半身不遂

3.hemicolloid [hemi- 半 + colloid n.& adj. 胶体（的）]
n. 半胶体

4.hemiparasite [hemi- 半 + n. 寄生物，寄生虫；]
n. 半寄生物