杨若惜的回答：

swine比pig较正式，pig可以说是昵称，就像鸽子我们可以叫pigeon,也可以叫dove，而书面语通常用pigeon。

梅涛的回答：

swine比pig较正式，pig可以说是昵称，就像鸽子我们可以叫pigeon,也可以叫dove，而书面语通常用pigeon。

陈天雨的回答：

swine is more formal than pig.

纤美媛的回答：

swine和pig还有hog,都是指猪，他们的区别： The words "swine," "hogs," and "pigs" refer to animals of the porcine family or pig family. The term swine can also refer to the pig family in a general way, and "pig" can be used in referencing young animals. "Hog" will generally refer to animals at or nearing market weight or finished for market.

安文华的回答：

swine （非正式）下流坯，猪猡 （旧指）猪 有贬义的意思