Usage of Chinese Number
Chinese grammar requires the use of classifiers (measure words) when a numeral is used together with a noun to express a quantity. For example, "three people" (三个人sān ge rén), is expressed as "three GE person", where 个gèis a classifier. There exist many different classifiers, for use with different sets of nouns, although 个is the most common, and may be used informally in place of other classifiers.
Chinese uses cardinal numbers in certain situations in which English would use ordinals. For example, 三楼means "third floor" (三楼sān lóu). Likewise, 二十一世纪is used for "21st century"(二十一世纪èrshí yī shìjì).
Numbers of years are commonly spoken as a sequence of digits, as in 二零零一("two zero zero one") for the year2001(二零零一èr líng líng yī). Names of months and days (in the Western system) are also expressed using numbers: 一月("one month") for January(一月yīyuè), etc.; and 星期一("week one") for Monday(星期一xīngqīyī), etc. (although Sunday is 星期日xīngqīrì, or informally 星期天xīngqītiān, "week day"). Full dates are usually written in the format 2001年1月20日for January 20, 2001 (using 年nián "year", 月yuè "month", and 日rì "day") – all the numbers are read as cardinals, not ordinals, with no leading zeroes, and the year is read as a sequence of digits.