Complex sentences

http://learnenglish.britishcouncil.org/en/english-grammar/clause-phrase-and-sentence/sentence-structure

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:

	Common conjunctions
Contrast clauses	although; though; even though; while;
Reason clauses	because; since; as
Place clauses	where; wherever; everywhere
Purpose clauses	so that; so; because + want
Result clauses	so that; so … that; such … that
Time clauses	when; before; after; since; while; as; as soon as; by the time; until
Conditional clauses	if; unless; provided (that); as long as