1.分隔并列的、3个以上的并行的数字、单词、短语或从句。如：

Water，sodium hydroxide，and ammonia were the solvents.

The red needles were collected，washed with toluene，and dried in a vacuum desiccator.

The deposit consists of clay，sand，and gravel.

注意：在该类表达中，“and”前面是否加逗号，所表达的含义是不同的。如：

The complex consists of three conformable，well-layered units of gabbro，diorite and granodiorite and granophyre.

这个“units”是由“（1）gabbro，（2）diorite，（3）granodiorite and granophyre”组成的？还是由“（1）gabbro，（2）diorite and granodiorite，（3）granophyre”组成的？含义不清。

2.分隔以数字或字母标识的一系列单词或短语。如：

Damage resulted from（1）vibration，（2）ground cracking，（3）subsidence，and（4）sea waves.

3.分隔不同级次的地名。如：

The specimens of species newly identified were deposited in the museum in Cairo，Egypt.

4.分隔相邻，但无关联的数据。如：

By the end of 1935，1000 experiments had been completed.

5.分隔在句子中间引导一系列单词或短语的that is，namely，for example，i.e.，e.g.等。例如：

The new derivatives obtained with the simpler procedure，that is，reaction with organocuprates，were evaluated for antitumor activity.

Alkali metal derivatives of organic compounds exist as aggregates of ion pairs，namely，dimers，trimers，and tetramers，in solvents of low polarity.

Many antibiotics，for example，penicillins，eephalosporins，and vancomycin，interfere with bacterial peptidoglycan construction.

These oxides are more stable in organic solvents（e.g.，ketones，esters，and ethers）than previously believed.

6.以“et al.”结尾的词条中，如有逗号或缩写点（句点）时，需用逗号分隔，否则免用逗号。如：

Saltzman，Brown，et al.

Saltzman，M.J.，et al.

但：“Saltzman et al.”中免用逗号。

7.分隔引导性单词、短语或从句。如：

Where data are inaccurate or insufficient，results deviate from what is expected.（如果表达为...are inaccurate or insufficient results deviate from...，句子的意思就会令人费解）

After cooling，the sample is reweighed and ground to 80 mesh.（不能表达为After cooling the sample is....）

Therefore，the type of organic solvent used is an important factor in lipase-catalyzed enzymatic synthesis.

After 3 months，the plants grown under phosphorus-deficient conditions were evaluated.

Although 40 different P450 enzymes have been identified，only six are responsible for the processing of carcinogens.

Because the gene and the molecular marker are so close on the chromosome，they segregate together in the progeny.

On cooling，a crystalline phase may develop in coexistence with an amorphous phase.

Deflected by natural obstructions，the lava stream turned eastward.

8.分隔非限制性从句或非限制性同位语，对于限制性从句或限制性同位语，则不用逗号分隔。如：

Switch A，which was on a panel，controlled the recording device.（非限制性从句）

The switch that stops the recording device also controls the light（限制性从句）

Raymond Turner，a mammalogist，described the 2 species.（非限制性同位语）

The species Bombyx mori is distinguished from other species by....（限制性同位语）

9.分隔以“such as”或“including”引导的非限制性短语，如若引导的是限制性短语，则不用逗号分隔。如：

Divalent metal ions，such as magnesium（Ⅱ）and zinc（Ⅱ），are located in the catalytic active sites of the enzymes.（非限制性短语，如果删除“such as magnesium（Ⅱ）and zinc（Ⅱ）”，并不影响句子的表达）

Hydrogen-bonded complexes，including proton-bound dimers，are wellknown species.（非限制性短语，如果删除“including proton-bound dimers”，并不影响句子的表达）

Potassium compounds such as KCl are strong electrolytes；other potassium compounds are weak electrolytes.（限制性短语，如果没有“such as KCl”，句子的意思就不清楚）

Previously，we described a mathematical model including a description of chlorophyll degradation in foods.（限制性短语，如果没有“including a description of chlorophyll degradation in foods”，句子的意思就不清楚）

10.多个并列形容词分别修饰同一个名词，并且调换形容词的顺序并不影响句子的意思时，形容词之间需使用逗号分隔；否则不能用逗号。如：

The intense，broad signals of the two groups confirmed their location.

Sample preparation is a repetitious，labor-intensive task.

A powerful，versatile tool for particle sizing is quasi-elastic light scattering.

但：(www.daowen.com)

Polyethylene is an important industrial polymer.

The rapid intramolecular reaction course leads to ring formation.

The local structural environment of the Mn cluster was determined.

11.分隔不同的参考文献序号，但如果是3个或3个以上连续的参考文献序号，则以en破折号（-）分隔，以上角标表示时，逗号后不加空格。如：

Experimental investigations10，14，18-25 concerned the relative importance of field and electronegativity effects.

Certain complexes of cobalt were reported（10，11）to have catalytic effects on hydrolysis reactions.

Flash photolysis studies（3-7）demonstrated the formation of transient inter-mediate products such as triplet states.

12.分隔正文中括号里所引文献的作者与年份。如：

...（Patrick，1993）.

13.分隔以for instance，together with，as well as，in addition to等引导的插入语或旁白。如：

A title or a headline，for instance，functions as a signal and determines our approach to the ensuing text.

The products，which were produced at high temperatures，were unstable.

Several individual flows，each thicker than 25 meters，have been traced for more than 160 kilometers.

但：Despite the pause the run was successful.（如改为Despite the pause，...并无助于清楚表达）

14.复合句应视其复杂程度和子句长度情况，决定是否采用逗号。如：

无逗号：Where the drainage went is problematical but it almost certainly turned west.

加逗号：A south-flowing course toward the White River looks plausible on a planimetric map，but geomorphic evidence is against it.

但：并列连词“for”和“as”前需加逗号，以免读者误认其为介词，如果用“because”取代“for”和“as”，则可省略逗号。如：

错误：The arching of the deck probably pulled the piling upward for the connections between the stringers and the piles were strong.

正确：The arching of the deck probably pulled the piling upward，for the connections between the stringers and the piles were strong.

或：The arching of the deck probably pulled the piling upward because the connections between the stringers and the piles were strong.

15.分隔表示对比关系的单词、短语或独立子句。如：

It is orange，not red.

The greater the risks，the greater will be the probable gain from the treatment.

16.分隔复合句中包含有连词引导的独立从句。如：

The reaction proceeds smoothly，and by use of appropriate reagents，the yields will be enhanced.

但：如果句子中只有两个并列的复合谓语或简短子句时，不用逗号分隔。如：

The product distribution results were obtained in sodium hydroxide and are listed in Table 10.

The survey was completed and we went home.

17.在并列连词（and，or，nor，but，yet，for，so）前使用逗号分隔各分句。如：

Toluene and hexane were purified by standard procedures，and benzene was redistilled from calcium hydride.

The role of organic templates in zeolite synthesis has been studied extensively，but no general principles have been delineated.

Supported metals are among the most important industrial catalysts，yet only a few have been studied thoroughly.

No dielectric constants are available for concentrated acids，so it is difficult to give a quantitative explanation for the results.

Field relations indicate divergent geomorphic histories for the two formations，yet over broad areas they are nearly coextensive.

18.用逗号引导直接引语。如：

In the words of Pasteur，“Chance favors the prepared mind.”

Pasteur said，“Chance favors the prepared mind.”

19.在对话的名词或短语后面。如：

Mr.Chairman，I will reply to the gentleman later.

20.在以“月、日、年”为次序排列的日期间使用逗号，但是，在以“日、月、年”为次序排列的日期间，则不使用逗号。如：

Martin Luther King，Jr.，was born on January 15，1929，and died on April 4，1968.

Martin Luther King，Jr.，was born on 15 January 1929 and died on 4 April 1968.

The events of July 1789 are as familiar to the French as those of July 1776 are to Americans.

The river flooded between March 6 and April 15，1975.