Although the weather is not very good today, what is behind it?

Although the weather is not very good today, I am in a good mood.

Related words are generally divided into turning relations, hypothetical relations and conditional relations. Combining two or more sentences that are closely related in meaning is called a complex sentence, also called a related sentence. Compound sentences are usually connected by some related words.

For some related words used in pairs, the first one can be omitted according to the situation, such as "not only … but also" "although … but" and "although" can be omitted. But in general, the "and" but "of the latter cannot be omitted. If only the former relative word is used and the latter relative word is omitted, the relationship between sentences will be unclear and the meaning of sentences will be unclear.