X

英 [eks] 美

X: The entire entry for X in Johnson's dictionary (1756) is: "X is a letter, which, though found in Saxon words, begins no word in the English language." Most English words beginning in -x- are of Greek origin or modern commercial coinages. East Anglian in 14c. showed a tendency to use -x- for initial sh-, sch- (such as xal for shall), which didn't catch on but seems an improvement over the current system. As a symbol of a kiss on a letter, etc., it is recorded from 1765. In malt liquor, XX denoted "double quality" and XXX "strongest quality" (1827).

Algebraic meaning "unknown quantity" (1660 in English, from French), sometimes is said to be from medieval use, originally a crossed -r-, in that case probably from Latin radix (see root (n.)). Other theories trace it to Arabic (Klein), but a more prosaic explanation says Descartes (1637) took x, y, z, the last three letters of the alphabet, for unknowns to correspond to a, b, c, used for known quantities.

Used allusively for "unknown person" from 1797, "something unknown" since 1859. As a type of chromosome, attested from 1902 (first so called in German; Henking, 1891). To designate "films deemed suitable for adults only," first used 1950 in Britain; adopted in U.S. Nov. 1, 1968. The XYZ Affair in American history (1797) involved French agents designated by those letters.
x (v.): "cross out with an 'X'," 1942, from X.

1. I had to go back for my checkup; they'd lost my X-rays.: 我得回去再做一次体检。他们把我的X光片弄丢了。

2. A stupid medical clerk had slipped the wrong tab on his X-ray.: 一个蠢笨的医护人员一不留神在他的X光片上贴错了标签。

4. The airline had been screening baggage on X-ray machines.: 该航空公司已采用X光机对行李进行安全检查。

5. They took my pulse, took my blood pressure, and X-rayed my jaw.: 他们给我量了脉搏、血压，还给我的下颌拍了X光片。