When do we use the coordinating conjunction NOR?

It's used to present a second negative idea to join a negative idea in the first clause. " Nor" is less common than other coordinating conjunctions, but still joins two (negative) ideas together.

Explanation:

in the 1890s, southern states enacted a new form of black codes, called “jim crow” laws. these laws made it illegal for blacks and whites to share public facilities. this meant that blacks and whites had to use separate schools, hospitals, libraries, restaurants, hotels, bathrooms, and drinking fountains.

explanation:

sentences vary by structure as well as by function. there are compound, complex, and compound-complex sentences.

simple sentence

i like to read.

a simple sentence has one independent clause.

compound sentence

i like to read, and i also like to write.

a compound sentence includes more than one independent clause, connected by a coordinating conjunction (and, but, for, nor, or, so, or yet).

complex sentence

i prefer to read books that are bestsellers.

a complex sentence includes one independent clause and one or more dependent clauses. (a dependent clause is one that cannot stand alone.) types of dependent clauses include relative clauses (i kicked the boy who pinched me), adverb clauses (i am going home now because i have a curfew), and noun clauses (i don't know what to do next).

compound-complex sentence

although i prefer to read current bestsellers, i do like to read old agatha christie mysteries, and i also like some 20th-century science fiction.

compound-complex sentences take a bunch of clauses (multiple independent clauses, and one or more dependent clauses) and toss them together like a salad. although these sentences take practice to write in a grammatically correct fashion, they can hold a tremendous amount of meaning, and are common in academic writing.