由 can be a noun,a prep.and a verb. 1,as a noun,由means reason or cause When it be used as a noun,in morden Chinese,we usually combine 由 with other Chinese characters to become a word gourp(phrase) such as 原由（yuán yóu），理由（lǐ yóu） in fact,these word groups mean reason or cause. 2, as a prep,由 means from,due to，because of,thanks to ect. When it means from ,it can be used as separately eg: 石头由山上落下来（Stones came down from the mountain.) When it means because of,thanks to ect.it must be combined with other Chinese characters in modern chinese. such as 由于(means because of,thanks to,this word can be used as a derogatory sense word or acommendatory sense word) eg: The accident was due to careless driving（这场车祸是由于粗心驾驶造成的。) 3,as a verb,由means leave or entrust something to someone.it can be used as a single Chinese character 这件事由你负责（You are responsible for this matter) --------------------- 又 can be used as a adv.or a conj. when it be uesd as a adv. it means once again, also, again eg:乔来了, 又喝醉了.(Here comes Joe, drunk again.) and as a conj. 又means both ... and eg:他既是一个战士又是一个诗人。(He is both a soldier and a poet．) You can find when it used as a conj.there is a phrase:既（jì) ……又 in english this phrase means both ... and In fact,learning Chinese word groups is more important than recite Chinese characters.because different Chinese characters in different word group its meaning will change.

由 has several main meanings as follows: 1. reason. e.g. 原由，由于。 2. from. 由表及里。由衷。 3. obey or follow. 又 means again. these two words doesn't have anything in common i女respect of meaning. Please pay attention to the pronunciation. 由 you2 first tone 又 you4 fourth tone I give you some examples of them. 由 你要给我一个理由。 我由衷地感谢你。 很多事故由粗心造成。 她由一个小姑娘长成了一个大美女。 又 我又迟到了。 爸爸又没回来。 I hope it is useful. for more infomation, please visit http://orichinese.com

由 has several main meanings as follows: 1. reason. e.g. 原由，由于。 2. from. 由表及里。由衷。 3. obey or follow. 又 means again. these two words doesn't have anything in common i女respect of meaning. Please pay attention to the pronunciation. 由 you2 first tone 又 you4 fourth tone I give you some examples of them. 由 你要给我一个理由。 我由衷地感谢你。 很多事故由粗心造成。 她由一个小姑娘长成了一个大美女。 又 我又迟到了。 爸爸又没回来。 I hope it is useful. for more infomation, please visit http://orichinese.com

You should put these two words in sentence. and then I can answer you accurately. If you just got them out of text. I only can answer like this: 由=as, 又= again.