Sentence Structure 

Simple sentences:

A simple sentence has only one clause :

The children were laughing.
John wanted a new bicycle.
All the girls are learning English.

Compound sentences:

A compound sentence has two or more clauses :

(We stayed behind) and (finished the job)
(We stayed behind) and (finished the job), then (we went home)

The clauses in a compound sentence are joined by co-ordinating conjunctions :

John shouted and everybody waved.
We looked everywhere but we couldn’t find him.
They are coming by car so they should be here soon.

The common coordinating conjunctions are:

and – but – or – nor – so – then – yet

Complex sentences:

A complex sentence has a main clause and one or more adverbial clauses . Adverbial clauses usually come after the main clause:

Her father died when she was very young
>>>
Her father died (main clause)
when (subordinating conjunction)
she was very young (adverbial clause)

She had a difficult childhood because her father died when she was very young.
>>>
She had a difficult childhood (main clause)
because (subordinating conjunction)
her father died (adverbial clause)
when (subordinating conjunction)
she was very young (adverbial clause).

Some subordinate clauses can come in front of the main clause:

Although a few snakes are dangerous most of them are quite harmless
>>>
Although (subordinating conjunction)
some snakes are dangerous (adverbial clause)
most of them are harmless (main clause).

A sentence can contain both subordinate and coordinate clauses:

Although she has always lived in France, she speaks fluent English because her mother was American and her father was Nigerian
>>>
Although (subordinating conjunction)
she has always lived in France (adverbial clause),
she speaks fluent English (main clause)
because (subordinating conjunction)
her mother was American  (adverbial clause)
and (coordinating conjunction)
her father was Nigerian (adverbial clause).

There are seven types of adverbial clauses: