Conjunctions are used to combine two clauses together. There are independent (main) and dependent (subordinate) clauses. Independent clauses are combined using a coordinating conjunction (koordinierende Konjunktion), which does not alter the word order of the joined clauses. Dependent clauses, however, are combined with independent clauses to form complete sentences using subordinating conjunctions (subordinierende / unterordnende Konjunktion). These conjunctions change the word order of the dependent clauses they appear in by shifting the conjugated (finite) verb to the end of the clause (not necessarily the end of the whole sentence; for example, if the sentence begins with a dependent clause).
The coordinating conjunctions are:
*This sentence can be shortened as follows: Es ist nicht spät sondern früh.
Some of the subordinating conjunctions are (not an exhaustive list):
Subordinating conjunctions in German change the word order of a sentence. Whereas with a coordinating conjunction, the conjunction is placed after the comma separating the two clauses being joined together and the subject then verb come next, when using a subordinating conjunction, the verb is moved out of second position and placed in the final position of the clause in which the conjunction is found. For example:
Sie möchte nach Hause gehen, denn sie ist sehr müde.
Sie möchte nach Hause gehen, weil sie sehr müde ist.
The verb (bold) is in the expected second position in the first example (using the coordinating conjunction ‘denn’ (underlined)) and in the final position in the second (using the subordinating conjunction ‘weil’ (also underlined)). Both conjunctions mean ‘because,’ but only ‘weil’ forces the verb to the end of the clause. Also, be aware that a subordinate clause can be extended by way of a coordinating conjunction, but this does not change the fact that the verb is placed at the end of the respective clauses (the subordinate word order continues throughout the combined dependent clauses).
Sie möchte nach Hause gehen, weil sie sehr müde ist und keine Energie mehr hat.
As shown above, the insertion of ‘und’ does not alter the word order after ‘weil.’ Furthermore, it is the conjugated verb — specifically — that goes at the end of the subordinate clause, as some clauses contain multiple verbs (e.g. helping verbs, modal verbs, infinitives), as seen here:
Weil sie nach Hause gehen möchte, sollte sie ihre Arbeit schneller machen.
Whenever you begin a sentence with a dependent/subordinate clause, the conjugated verb of the independent clause must come immediately after the comma separating the two halves of the sentence.