Choices in punctuation can greatly affect meaning. Indeed if you mess with punctuation enough you can turn the meaning upside down:  

1．下雨天留客天留我不留

2．从中学到大学都学不到的东西

3．世界上女人没有了男人就不能生活了

4． Eats shoots and leaves

5.  An English teacher wrote these words on the whiteboard: "woman without her man is nothing". The teacher then asked the students to punctuate the words correctly.

6. dear john I want a man who knows what love is all about you are generous kind thoughtful people who are not like you admit to being useless and inferior you have ruined me for other men I yearn for you I have no feelings whatsoever when were apart I can be forever happy will you let me be yours Gloria

If you have ever wondered if punctuation is truly important, try reading a passage that does not have punctuation. It is nearly impossible to correctly figure out what the writer was trying to say. Punctuation tells us when one idea stops and another starts. It tells use who owns things and who said what. Punctuation helps us to understand what we are reading.

The most common mistake people tend to make while writing is in the use of Punctuation. Wrong punctuation can damage the flow of ideas and change meaning, but properly used punctuation not only helps readers understand your meaning but also makes them engrossed in your writing. The following discussion is about some of the frequently misused punctuation marks and what actually their correct application should be.

Punctuation helps readers break writing into logical units, making it easier to follow. Punctuation includes all the conventional signs used to separate words: spaces, first-line indentation of paragraphs, blank lines, uppercase letters, and various marks or stops （commas, periods, semicolons, and so on）. Punctuation is conventional rather than scientific, and has evolved over time. The earliest written languages, in fact, had no punctuation at all, writers just RANWORDSTOGETHERFORASLONGASTHEYCAREDTOWRITE （every so often a bold pioneer would introduce a reader-friendly innovation like LowerCaseLetters or spaces between words）.

In the modern world punctuation is an important thing to get right in formal writing. Readers of formal writing interpret punctuation mistakes as a sign of poor education or carelessness, and in either case tend to discount the work's validity.