Examples: 1. When I take a day off from work, I like to stay home and relax. 2. When it's hot outside, I usually stay inside. 3. When my brother helps me with my math homework, I usually get an "A." 4. When the traffic light turns green, I put my foot on the gas pedal. 5. When a student asks a question, it's important for his teacher to answer it clearly.
Notice that the words before the comma in each of the first four examples above can be moved to the end of the sentence.
1. I like to stay home and relax when I take a day off from work. 2. I usually stay inside when it's hot outside. 3. I usually get an "A" when my brother helps me with my math homework. 4. I put my foot on the gas pedal when the light turns green.
In Example #5, however, A few words must be changed. 5. It's important for a teacher to answer clearly when a student asks a question.
Conclusions: A. When you use "when," you set up a condition. When the condition is true, then the other part of the sentence (the result clause) becomes relevant. If your condition is never true, the result clause never takes effect.
B. When you use "when" with a present tense verb, you are saying that something happens regularly or you are making a general statement (that may or may not be true).
C. The part of the sentence that includes "when" can go either at the beginning or the end of a sentence.