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If Vs. When

In conditional statements, ‘if’ and ‘when’ can be used interchangeably – but only in certain cases.  In certain other cases, using ‘when’ instead of ‘if’ will result in idiomatically incorrect sentence. In this post, I will explain when ‘if’ and ‘when’ can be used interchangeably and when they cannot be.

When in conditional statements can ‘if’ and ‘when’ be used inter-changeably?

‘If’ and ‘when’ can be used interchangeably when we present conditions in which the outcome is definite or the outcome is a general fact. i.e. if event A happens, event B happens.

  1. Example 1 – We know as a general fact that water evaporates when it is heated.
    • If you heat water, it evaporates. – CORRECT
    • When you heat water, it evaporates. – CORRECT
  2. Example 2 – We know based on past experience that Tom loses weight when he exercises.
    • Considering his past successes in losing weight, Tom knows that if he exercises, he loses weight. – CORRECT
    • Considering his past successes in losing weight, Tom knows that when he exercises, he loses weight. – CORRECT

Learn when to use ‘due to’ and ‘because of’

When can you not use ‘when’ in place of ‘if’?

When ‘if’ conditional statement is used to express a situation in which the outcome is a possibility and not a certainty, ‘when’ cannot be used in place of ‘if’.

  1. Example 1 – Possibility of going to fair
    • Morgans may go to the fair, if the weather is bright and sunny. – CORRECT
    • Morgans may go to the fair, when the weather is bright and sunny. – INCORRECT
  2. Example 2 – Tom is not certain if by exercising he will lose weight or not.
    • Considering his not so high success rate in losing weight, Tom knows that if he exercises, he may lose weight. – CORRECT
    • Considering his not so high success rate in losing weight, Tom knows that when he exercises, he may lose weight. – INCORRECT

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How do you know if the conditional statement describes a definite outcome or a possibility?

The context of the sentence sets the tone of the conditional statement.  In the examples for probable outcomes,  the sentence clearly states that Tom has not been very successful in losing weight.  Thus, its only a possibility that he loses weight upon exercising.  Hence the conditional statement expresses a possibility and not a certainty.

How does GMAT test this concept?

In OG12 Question # 12, GMAT tests this concept.  In 3 choices ‘when’ is used to express a conditional statement in which the outcome is a possibility.  The correct choice uses ‘if’ to correctly express the statement.  For more details on this question click here.

What are the key takeaways?

  1. If the conditional statement expresses a general fact ‘if’ and ‘when’ can be used interchangeably.
  2. If the conditional statement expresses a possibility, ‘when’ cannot be used in place of ‘if’.

To learn more about conditional statements covered in the e-GMAT SC course, click here.

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