The purpose of a compare and contrast essay is to analyze the differences and/or the similarities of two distinct subjects. A good compare/contrast essay doesn’t only point out how the subjects are similar or different (or even both!). It uses those points to make a meaningful argument about the subjects. While it can be a little intimidating to approach this type of essay at first, with a little work and practice, you can write a great compare-and-contrast essay!

 Develop your thesis

There are many directions a compare-and-contrast thesis can take, but it should always make an argument that explains why it’s useful to put these two subjects together in the first place. A good compare and contrast essay will help your readers understand why it’s useful or interesting to put these two subjects together.(抓重點：argument)

寫一篇比較事物的文章的目標不是比較，而是你為什麼去做比較，你比較是要為了得到什麼結論，你的比較能揭示什麼，意義何在。所以一篇好的比較文應該開頭就給出論據或是說你的topic，只有這樣你後面才能圍繞一箇中心展開你的比較，你的比較才具備了意義。給幾個例子：

1. Show readers why one subject is more desirable than the other. Example: "Cats are better pets than dogs because they require less maintenance, are more independent, and are more adaptable."（這類開頭的文章告訴我們，這篇文章純粹是表達作者態度、立場、偏好的一篇文章）
2. Help readers make a meaningful comparison between two subjects. Example: "New York City and San Francisco are both great cities for young professionals, but they differ in terms of their job opportunities, social environment, and living conditions."
3. Show readers how two subjects are similar and different. Example: "While both The Catcher in the Rye and To Kill a Mockingbird explore the themes of loss of innocence and the deep bond between siblings, To Kill a Mockingbird is more concerned with racism while The Catcher in the Rye focuses on the prejudices of class."（同樣都是similarity and difference為什麼人家的就可以寫在開頭，我的就不可以呢？注意，這裡的異同是挖深了的異同，而不是我們一眼就可以看出來的，是需要後文大量基礎的比較做支撐的，當然人家就檔次高了）
4. In middle school and high school, the standard format for essays is often the “5-paragraph form,” with an introduction, 3 body paragraphs, and a conclusion. If your teacher recommends this form, go for it. However, you should be aware that especially in college, teachers and professors tend to want students to break out of this limited mode. Don’t get so locked into having “three main points” that you forget to fully explore your topic.

  Organizing Your Essay

1 Decide on a structure

There are several ways to organize a compare-and-contrast essay. Which one you choose depends on what works best for your ideas. 

• Subject by subject. This organization deals with all of the points about Topic A, then all of the points of Topic B. This style of writing can be helpful if you are using one subject as a “lens” through which to examine the other.  

• Point by point. This type of organization switches back and forth between points. For example, you could first discuss the prices of frozen pizza vs. homemade pizza, then the quality of ingredients, then the convenience factor. The advantage of this form is that it’s very clear what you’re comparing and contrasting. The disadvantage is that you do switch back and forth between topics, so you need to make sure that you use transitions and signposts to lead your reader through your argument.

• Compare then contrast. This organization presents all the comparisons first, then all the contrasts. It’s a pretty common way of organizing an essay, and it can be helpful if you really want to emphasize how your subjects are different.

這裡依次貼上三種style的結構圖示：

2 Outline your essay

Outlining your essay will help you work out the main organizational structure and will give you a template to follow as you develop your ideas. No matter how you decided to organize your essay, you will still need to have the following types of paragraphs:

這裡著重講一下最後兩點

Acknowledgement of other Arguments: This paragraph acknowledges that other counter-arguments exist, but discusses how those arguments are flawed or do not apply.

Conclusion. This paragraph summarizes the evidence presented. It will restate the thesis, but usually in a way that offers more information or sophistication than the introduction could. Remember: your audience now has all the information you gave them about why your argument is solid. They don’t need you to just reword your original thesis. Take it to the next level! （這是蒟蒻覺得最難的地方。。。）

3 Something to be noticed

Once you've chosen an organizational method for your body paragraphs, you'll need to have an internal organization for the body paragraphs themselves. Each of your body paragraphs will need to have the three following elements:

• Topic sentence: This sentence introduces the main idea and subject of the paragraph. It can also provide a transition from the ideas in the previous paragraph.
• Body: These sentences provide concrete evidence that support the topic sentence and main idea.
• Conclusion: this sentence wraps up the ideas in the paragraph. It may also provide a link to the next paragraph’s ideas.

  Putting It All Together

1 Use your brainstorming ideas to fill in your outline. 

Once you’ve outlined your essay, it should be fairly simple to find evidence for your arguments. Look at the lists and diagrams you generated to help you find the evidence for your comparisons and contrasts.

• If you are having trouble finding evidence to support your argument, go back to your original texts and try the brainstorming process again. It could be that your argument is evolving past where it started, which is good! You just need to go back and look for further evidence.

2 Remember to explain the “why.”

A common error many writers make is to let the comparisons and contrasts “speak for themselves,” rather than explaining why it’s helpful or important to put them together. Don’t just provide a list of “ways Topic A and Topic B are similar and different.” In your body paragraphs as well as your conclusion, remind your readers of the significance of your evidence and argument.

• For example, in a body paragraph about the quality of ingredients in frozen vs. homemade pizza, you could close with an assertion like this: “Because you actively control the quality of the ingredients in pizza you make at home, it can be healthier for you than frozen pizza. It can also let you express your imagination. Pineapple and peanut butter pizza? Go for it! Pickles and parmesan? Do it! Using your own ingredients lets you have fun with your food.” This type of comment helps your reader understand why the ability to choose your own ingredients makes homemade pizza better.

3 Come up with a title. 

“Essay Number One” may say exactly what the paper is, but it’s not going to win any points for style. A good essay title will preview something about the paper’s argument or topic. Depending on your audience and the situation, you may make a joke or a pun, ask a question, or provide a summary of your main point.

  Method to improve your essay

1 Take a break. 

One of the most common mistakes student writers make is to not give themselves enough time to take a step back from their essays for a day or two. Start early so that you can let your finished draft sit for a day, or at least a few hours. Then, come back to it with fresh eyes. You’ll find it easier to see holes in your logic or organizational flaws if you’ve had time to take a break.

• Reading your essay aloud can also help you find problem spots. Often, when you’re writing you get so used to what you meant to say that you don’t read what you actually said.

2 Review your essay. 

Look out for any grammatical errors, confusing phrasing, and repetitive ideas. Look for a balance in your paper: you should provide about the same amount of information about each topic to avoid bias. Here are some things to consider before you turn in your paper:

• Avoid bias. Don't use overly negative or defamatory language to show why a subject is unfavorable; use solid evidence to prove your points instead.
• Avoid first-person pronouns unless told otherwise. In some cases, your teacher may encourage you to use “I” and “you” in your essay. However, if the assignment or your teacher doesn’t mention it, stick with third-person instead, like “one may see” or “people may enjoy.” This is common practice for formal academic essays.
• Proofread! Spelling and punctuation errors happen to everyone, but not catching them can make you seem lazy. Go over your essay carefully, and ask a friend to help if you’re not confident in your own proofreading skills.

  Good Example

NCE Lesson 41: Illusions of Pastoral peace 

The quiet life of the country has never appealed to me. City born and city bred. I have always regarded the country as something you look at through a train window, or something you occasional visit during the weekend. Most of my friends live in the city, yet they always go into raptures3 at the mere4 mention of the country. Though they extol5 the virtues6 of the peaceful life, only one of them has ever gone to live in the country and he was back in town within six months. Even he still lives under the illusion that country life is somehow superior to town life. He is forever talking about the friendly people, the clean atmosphere, the closeness to nature and the gentle pace of living. Nothing can be compared, he maintains, with the first cockcrow, the twittering of birds at dawn, the sight of the rising sun glinting on the trees and pastures. This idyllic7 pastoral scene is only part of the picture. My friend fails to mention the long and friendless winter evenings in front of the TV -- virtually the only form of entertainment. He says nothing about the poor selection of goods in the shops, or about those unfortunate people who have to travel from the country to the city every day to get to work. Why people are prepared to tolerate a four-hour journey each day for the dubious8 privilege of living in the country is beyond me. They could be saved so much misery9 and expense if they chose to live in the city where they rightly belong.

If you can do without the few pastoral pleasures of the country, you will find the city can provide you with the best that life can offer. You never have to travel miles to see your friends. They invariably live nearby and are always available for an informal chat or an evening's entertainment. Some of my acquaintances in the country come up to town once or twice a year to visit the theatre as a special treat. For them this is a major operation which involves considerable planning. As the play draws to its close, they wonder whether they will ever catch that last train home. The city dweller never experiences anxieties of this sort. The latest exhibitions, films, or plays are only a short bus ride away. Shopping, too, is always a pleasure. There is so much variety that you never have to make do with second best. Country people run wild when they go shopping in the city and stagger home loaded with as many of the exotic items as they can carry. Nor is the city without its moments of beauty. There is something comforting about the warm glow shed by advertisements on cold wet winter nights. Few things could be more impressive than the peace that descends11on deserted12 city streets at weekends when the thousands that travel to work every day are tucked away in their homes in the country. It has always been a mystery to me why city dwellers13, who appreciate all these things, obstinately14 pretend that they would prefer to live in the country.

  My essay for practice

Why I prefer living on campus?

It's the question that every college student must answer: should you live on-campus or off-campus? Both options have pros and cons, so it is crucial to weigh your choices before make a final decision. As for me, my preference will be the first one.

Convenience must be the first factor for my choice. Living on campus, you can easily walk to classes, libraries, computer labs, cafeterias, etc, while living off campus means you have to wake up early in the morning to get to school in case of being late for classes. When it comes to expenses, living off campus can be at an absolute disadvantage. Monthly rent payments, utility bills, and grocery shopping will come to disturb you from time to time. What a miserable life it will be if one is to agonize over both school work and daily expenses. What's more, dormitory life is effective to prevent you from loneliness. Roommates are invariable nearby and are always available for an informal chat or an evening's entertainment. Provided that you live off campus, the only way to drive the isolation away may be chatting with individuals in the virtual world.

As the saying goes, one can never miss a campus life, and so do I.

ps: 本篇博文主要參考wikiHow的 How to Write a Compare and Contrast Essay，博主主要摘錄出了自己平時寫作容易忽視的點（實在不知道怎麼寫作 _(:з」∠)_