Conditional Sentences

Definition:
A type of adverbial clause that states a hypothesis or condition, real or imagined.
A conditional clause may be introduced by the subordinating conjunction if or another conjunction, such as unless, provided that, or in case of.
Like other adverbial clauses, a conditional clause can come either before or after the clause on which it states a condition

Examples and Observations:

• "If you want a friend in Washington, get a dog."
  (Harry Truman)



• "If we had no winter, the spring would not be so pleasant; if we did not sometimes taste of adversity, prosperity would not be so welcome."
  (Anne Bradstreet, "Meditations Divine and Moral")



• "Romans park their cars the way I would park if I had just spilled a beaker of hydrochloric acid on my lap."
  (Bill Bryson, Neither Here Nor There: Travels in Europe. William Morrow, 1992)

• "If I had only known, I would have been a locksmith."
  (Albert Einstein)



• "Conditions deal with imagined situations: some are possible, some are unlikely, some are impossible. The speaker/writer imagines that something can or cannot happen or have happened, and then compares that situation with possible consequences or outcomes, or offers further logical conclusions about the situation."
  (R. Carter, Cambridge Grammar of English. Cambridge Univ. Press, 2006)



• Types of Conditional Clauses
  There are six main types of conditional sentence:
  1. For example, the equilibrium between liquid and vapor is upset if the temperature is increased.
     (General rule, or law of nature: it always happens.)
  
  
  2. If you start thinking about this game, it will drive you crazy.
     (Open future condition: it may or may not happen.)
  
  
  3. But if you really wanted to be on Malibu Beach, you'd be there.
     (Unlikely future condition: it probably won't happen.)
  
  
  4. If I were you, I would go to the conference center itself and ask to see someone in security.
     (Impossible future condition: it could never happen.)

5. "I would have resigned if they had made the decision themselves," she said.
   (Impossible past condition: it didn't happen.)


6. If he had been working for three days and three nights then it was in the suit he was wearing now.
   (Unknown past condition: we don't know the facts.)

(John Seely, Grammar for Teachers. Oxpecker, 2007)