English learners

[ Expressing the future in time clauses] (a) Bob will come soon. when Bob comes, we will see him. (b) Linda is going to leave soon. Before she leaves, she is going to finish her work. (c) I will get home at 5:30. After I get home, I will eat dinner. (d) The taxi will arrive soon. As soon as it arrives, we will be able to leave for the airport. (e) They are going to come soon. I will wait here until they come. (f) While I am traveling in Eruope next year, I am going to save money by staying in youth hostels. (g) I will go to bed after I finish my work. (h) I will go to bed after I have finished my work. In (a) when Bob comes is a time clause.
When +subject + verb= a time clause. Will or be going to is not used in a time clause. The meaning of clause is future, but the simple present tense is used. A time clause begins with such words as when. Before, after, as soon as, until, while and includes a subject and a verb. The time clause can come either at the beginning of the sentence or in second part of the sentence. When he comes, we will see him. Or
We will see him when he comes. Sometimes the present progressive is used in a time clause to express an activity that will be in progress in the future, as in (f). Occasionally, the present perfect is used in a time clause, as in (h). Examples (g) and (h) have the same meaning. The present perfect in the time clause emphasizes the completion of the act before the other act occurs in the future.