Use Reduced Adverb Clauses Correctly

Adverb clauses can also appear in a reduced form. In the reduced form, the adverb connector remains, but the subject and be-verb are omitted.

Although he is rather unwell, the speaker will take part in the seminar.
When you are ready, you can begin your speech.

These two examples may be used in either the complete or reduced form.
In the reduced form, the adverb connectors although and when remain; the subjects he and you as well as the be-verbs is and are are omitted.

If there is no be-verb in the adverb clause, it is still possible to have a reduced form. When there is no be-verb in the adverb clause, the subject is omitted and the main verb is changed into the -ing form.

Although he feels (feeling) rather sick, the speaker will take part in the seminar.
When you give (giving) your speech, you should speak loudly and distinctly.

In the first example, the adverb clause although he feels rather sick does not include a be-verb; to reduce this clause, the subject he is omitted and the main verb feels is changed to feeling. In the second example, the adverb clause when you give your speech also does not include a be-verb; to reduce this clause, the subject you is omitted and the main verb give is changed to giving.

The following example shows how this sentence pattern could be tested in structure questions on the TOEFL test:

Example from the Paper and Computer TOEFL® Tests
When ___, you are free to leave.
(A) The finished report
(B) Finished with the report
(C) The report
(D) Is the report finished

In this example, you should note the adverb connector when, and you should know that this word could be followed by either a complete clause or a reduced clause. Answers (A) and (C) contain the subjects the finished report and the report and no verb, so these answers are incorrect. In answer (D), the subject and verb are inverted, and this is not a question, so answer (D) is incorrect. The correct answer is (B); this answer is a reduced adverb clause that means when you are finished with the report.

It should be noted that not all adverb clauses can appear in a reduced form, and a reduced adverb clause can only be reduced if the verb is in the passive form.

Once you submit your thesis, you will graduate. → (active — does not reduce)
Once it is submitted, your thesis will be reviewed. → (passive — does reduce)

In the first example, the adverb clause once you submit your thesis does not reduce because clauses introduced by once only reduce if the verb is passive, and the verb submit is active. In the second example, the adverb clause once it is submitted does reduce to once submitted because the clause is introduced by once and the verb is submitted is passive.