电气工程专业英语常用符号和公式表达.doc

2.4 常用符号和公式表达(Symbols and Formulas in English for Special Science and Technology)2.4.1国际单位制中的前缀，特殊符号与常用希腊字母专业英语中的物理量采用国际单位制（International System of units）SI，当表示更大或更小的量时，为方便和简单起见，经常在基本的国际单位前面加上词头。国际单位制中的前缀（SI prefixes）前缀符号数值中文名称例词tera-T1012兆兆（亿万）giga-G109千兆（十亿）GHz 10kHz1GHzmega-M106兆kilo-k103千kilometer千米（km） kilovolt千伏（kV）kilowatt 千瓦(kW) kilogram千克（kg）hecto-h102百deca-da101十deci-d10-1分（十分之一）centi-c10-2厘centimetermilli-m10-3毫Milliampere毫安（mA） milliammeter毫安表micro-10-6微Microfarad微法拉（F）nano-n10-9纳nanometer纳米pico-p10-12微微femto-f10-15毫微微atto-a10-18微微微常用希腊字母（Frequently used Latin alphabet）alphabetagammadeltaepsilonetathetamupisigmatauphipsiomegalambda特殊符号（Special symbols）符号意义符号意义becauseis approximately equal tothereforeis not equal tois not greater than=is equal tois not less thaninfinityresult inat; print&andinches; secondsis less than or equal tominutes, feetis more than or equal tois perpendicular tois equivalent toplus or minus#number, integral, double , $dollar/is parallel to+plus; positivevaries asmultiplied by (times)is member of set￥yuanimplies()round bracketsIm(j)imaginary partsquare bracketsRe(j)real partminus; negative|x|the absolute value of xanglesemicirclecirclecircumferencetriangleintersection ofunion of(sigma) summation of2.4.2小数（decimal），分数（fraction），百分数(percent)小数0.1 : zero point one, point one, o point one, one tenth, decimal one0.01: point zero one, 10.35: ten point three five239.24: two hundred and thirty-nine point two four1/2: a(one)half 1/3: a third1/4: one quarter 1/8: a eighth2/3: two-thirds, two over three, two divided by three3/4: three-fourths, three quarters113/324: one hundred and thirteen over three hundred and twenty four4 2/3: four and two thirds3%: three percent52%: fifty-two percent0.2%: point two percent5: five per mill分数1/2a (one) half 1/3a (one) third1/4a (one) quarter 1/9a (one) ninth2/3two thirds3/16three sixteenths four and two-thirds基数1,001one thousand and one3,123,400three million, one hundred and twenty-three thousand and four hundred序数第2034 two thousand and thirty-fourth第900 nine-hundredth第134 hundred and thirty-fourth第10,000ten thousandth分数100%() one hundred per cent (mille)0.5%point five per cent0.46%point four six per cent2.05two point nought five; two point O five6.003six point nought nought three; six point O O three78.72 seventy-eight point one two号码62374881six two three seven four double-eight one400044 four triple zero double four日期在英式英语中，日期在前月份在后，即顺序为日月年，但在美式英语中，则月份在前日期在后，即顺序为月日年。这一点必须注意，否则会发生错误。例如我们写10-7-86或10/7/86，在英式英语中是July 10th 1986,而在美式英语中，则为October 7th 1986.我们使用的计算机上的时间就是美式英语。millennium千年 (来自拉丁语 mille千+annus年)2.4.3幂（power），根（root）: x square, x squared ,the square of x, the second power of x, x to the second power: y cube, y cubed, the cube of y, the third power of y, y to the third power: the nth power of a , a to the n power : the square root of three : the cube(third ) root of a: the nth root of a2.4.4数学符号(Mathematical symbols)A+BA and B, A plus B A-BA minus BABA times B, A multiplied by BABA over B, A divided by BABA plus or minus BA=BA equals B, a equals to b , a is equal to bABA is not equal to B, A is not BABA is approximately equal to BABA is greater than BABA is greater than BABA is much (far) greater than BA 7+312 is greater than 7 plus 372-16=56 72 minus 16 is 56x3/5=y2the third power of x (x cube) divided by (over)5 equals y square a equals V sub x minus V sub y over t(a +b - c d) e = fa plus b minus c multiplied by d, all divided by e equals f Big e equals to the ratio of p divided by a to e divided by l, is equals to the ratio of product of p.l to the product of a.e The integral of dy over (by) the square root of c square minus y square.M=R1x-P1(x-