digraph used in Old French for the "tsh" sound. In some French dialects, including that of Paris (but not that of Picardy), Latin ca- became French "tsha." This was introduced to English after the Norman Conquest, in words borrowed from Old French such as chaste, charity, chief (adj.). Under French influence, -ch- also was inserted into Anglo-Saxon words that had the same sound (such as bleach, chest, church) which in Old English still was written with a simple -c-, and into those that had formerly been spelled with a -c- and pronounced "k" such as chin and much.
As French evolved, the "t" sound dropped out of it, so in later loan-words from France ch- has only the sound "sh-" (chauffeur, machine (n.), chivalry, etc.).
It turns up as well in words from classical languages (chaos, echo, etc.). Most uses of -ch- in Roman Latin were in words from Greek, which would be pronounced correctly as "k" + "h," as in blockhead, but most Romans would have said merely "k." Sometimes ch- is written to keep -c- hard before a front vowel, as still in modern Italian.
In some languages (Welsh, Spanish, Czech) ch- can be treated as a separate letter and words in it are alphabetized after -c- (or, in Czech and Slovak, after -h-). The sound also is heard in more distant languages (as in cheetah, chintz), and the digraph also is used to represent the sound in Scottish loch.
实用例句
1. We are on the 356 radial CH DME 46.
我们在CH的356度方位,距离46海里.
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2. Press CH button to set the Channel Set Mode.
按CH按钮来设置频道设置方式.
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3. FT - IR shows DLC film comprises CH 3、 CH 2、 CH 、 Si - O - Si , Si - O - C and Si - CH 3 bond.
