所以：因为 and 所以 go together like peas in a pod. Typical cause-and-effect sentence. 因为 demonstrates cause, while 所以 does result. When the subject's the same in both parts of the sentence, it can be placed before 因为，after 因为，or after 所以。All are fine. But when the subjects are different, both can only be placed in front of the subject. Note: When the part of the sentence expressing the result is the first part, that is, 因为 is in the second part, then you can't use 所以 in the first part. For example: 他的汉语不太好，因为他刚学了两个月。 李明很喜欢去图书馆，因为他喜欢看书。 所以 can stand just fine on its own, without the echoing services of 因为。eg： 今天有朋友来，所以她要去机场接。 When you're telling a story, if you wanna drag out the "so..." people often say “所以呢。。。”

于是：this word is a bit more complicated. It solidifies the relationship between the parts of a sentence, and is generally used in its sentence part, either before or after the subject. Its main function is to connect the two parts of the sentence like superglue. The things the sentence in which it appears shows are frequently brought on by the first part, as such, it's the result of the development of whatever happened in the first sentence. eg: 听说这家服装公司正在招聘设计师，于是我就来报名了。 小王病得很厉害。于是，大家把他送进了医院。 工人们青睐了老专家，问题于是很快就解决了。 看到她哭得那么伤心，我于是决定留下来圈圈她。 走过一片农田，穿过一个小树林，于是静湖（Lake Jing）便（就）出现在眼前了。 We can break down the types of results that 于是 goes along with into these: 1. 于是 is a measure taken due to the circumstances of the first sentence. 清早起床，看到外面阳光灿烂，于是便约了大卫去爬山。（In the early morning after getting up, on seeing how bright the sunshine was, I then arranged to go mountain-climbing with Dawei) 2. 于是 is the development or reaction of the circumstances of the first part. 回家后，李平（Li Ping）越想越气，于是大哭了一场。(After returning home, the more Liping thought about it the madder she got, so she had herself a big cry). 3. 于是 is the result of a movement, basically getting to a new place. 过了一座山，又过了一条河，于是我家就在眼前了。(Once you pass a mountain, then cross a river, and my house is right there) 4. 于是 is often said as 于是乎, it carries a slight connotation of written Chinese. 从同学们的反应中他知道自己说错了话，于是乎，低头不语。From his classmate's reaction, he realized he'd said something wrong, so he therefore lowered his head and went silent.

Many of these connective words all mean roughly the same, but where they differ most in in their usage, that is, set patterns of usage that you can't go switching up willy-nilly. The English sentences, for the most part, relies on these connective words, and as such they are indispensable to the sentence but Chinese, much to our dismay, is much trickier in that these connective words are often left out, especially in oral language. Luckily, written Chinese usually will follow stricter patterns of usage, but the disparity between oral and written Chinese is definitely in my opinion one of the biggest hurdles in keeping straight while learning Chinese! Anyways: I'll transcribe the basics of each word from a reference book for ya. 由于：Conjunction, shows reason. It's used in the first part of a complex cause-and-effect sentence, the second part shows the result. It often has "所以、因此、因而” to echo it. For example: 由于时间太短，所以写得不好。 由于是第一次用，所以他不知道怎么用。 由于他的汉语说得太好了，因此很多人认为他是中国人，其实他是韩国人。 * When the subject in both parts of the sentence is the same, 由于 can be placed both before and after the subject. If they're different, then it can only be placed before it. 由于我们没有买到今天的飞机票，所以明天回去。 （雾由于太大，所有的船都停了）incorrect Compared with 因为： （1）因为 can be used in the sentence's second part, but 由于 can't. (他们和父母住在一起，因为他们还没有自己的房子）由于 is incorrect here (2) While 由于 often goes with 因此，因为 very infrequently does. (3) 由于 is used more in written Chinese, while 因为 is used both in oral and written.

因此：conjunction, shows result. 1. It's used in the second part of a complex cause-and-effect sentence, it can be used alone, or with 由于。When the subject is the same in both parts, 因此 can be used both in front of the subject and behind, but when they're different, it can only be used in front. For example: 听说下星期有歌唱比赛，因此我们班的同学这几天一直在排练。 2. When it's used in the middle of a sentence, 因此 often carries a negative word like 也、都、etc, the meaning thus becomes "because of this reason." For example: 他干活很小心，但是领带并不因此就表扬他。 今天是星期六，天气预报说有暴雨，但是很多人并不因此而不敢出门。(Today's Saturday, the weather forecast said there was gonna be downpours, but the reason why many people don't dare leave their homes is not because of this all) clunky sentence, but you get it 因此 and 因为： 1: 因为 can be a conjunction as well as a preposition, whereas 因此 can only be a conjunction. 2: When 因为 is a conjunction, what's connected afterwards is the reason, whereas what 因此 connects is the result. 3: 因此 can combine with 由于，but 因为 can't. 4: 因为 can be used in both oral and written Chinese, while 因此 is used much more in written Chinese.

由于means' because'. 因此and所以 is similar.They means' so'. 于是means that "lead to"