量和单位的名称、符号和书写规则应严格执行ＧＢ３１００～３１０２９３规定。１　量的符号一般为单个拉丁字母或希腊字母，并一律采用斜体（ｐＨ例外），如长度ｌ，质量ｍ，时间ｔ，压力ρ；为区别不同情况，可在量符号上附加角标，如相对原子质量Ａｒ，相对分子质量Ｍｒ， The amount and unit name, symbols and writing rules should be strictly enforced GB3100 ~ 3102  93 regulations. 1 The symbols are generally a single Latin or Greek letter, and are always in italics (pH exceptions), such as length l, mass m, time t, pressure ρ; in order to distinguish between different situations, Relative atomic mass Ar, relative molecular mass Mr,