subordinate clause/从句

What Is a Subordinate Clause? (with Examples)
A subordinate clause (or dependent clause) is a clause that cannot stand alone as a complete sentence because it does not express a complete thought.
Like all clauses, a subordinate clause has a subject and verb.

Examples of Subordinate Clauses
Here are some examples of subordinate clauses (shaded). You will notice that none of the shaded clauses could stand alone as a sentence. This is how a subordinate clause (or a dependent clause) is different from an independent clause.

• She had a pretty gift for quotation, which is a serviceable substitute for wit. (W Somerset Maugham, 1874-1965)
• A musicologist is a man who can read music but can't hear it. (Sir Thomas Beecham, 1879-1961)
• Always be nice to those younger than you because they are the ones who will be writing about you. (Cyril Connolly, 1903-1974)
• Personally I'm always ready to learn, although I do not always like being taught. (Sir Winston Churchill, 1874-1965)

Types of Subordinate Clause
Subordinate clauses can act as adjectives, adverbs, or nouns.

The Adjective Clause. Here is an example of a subordinate clause acting as an adjective:

• The bull that charged us is back in the field.
  (The subordinate clause that charged us describes the bull. It is an adjective clause.)

The Adverbial Clause. Here is an example of a subordinate clause acting as an adverb:

• I fished until the sun went down.
  (The subordinate clause until the sun went down modifies the verb to fish. It is an adverbial clause.)

The Noun Clause. Here is an example of a subordinate clause acting as a noun:

• Whoever dislikes the new timings is more than welcome to leave.
  (The subordinate clause Whoever dislikes the new timings is the subject of this sentence. It is a noun clause.)

ref:
http://www.grammar-monster.com/glossary/subordinate_clause.htm