Restrictive vs. nonrestrictive adjective clause

Q:

Is this sentence correct? Does it sound natural?

The limbs that are used for locomotion or grasping are outgrowths from the trunk.

Should there be a comma after "limbs"?

vera
vcqm@ruralsp.com.br
Posted 20 February 2003

The limbs that are used for locomotion or grasping are outgrowths from the trunk.

This sentence is fine if the relative clause "that are used for locomotion or grasping" is essential to the description of these limbs. It implies that there are other limbs, as in this passage:

(a)	A bobbledoo has six limbs. The limbs that are used for locomotion or grasping are outgrowths from the trunk; the limbs used to direct poisonous substances at aggressors are outgrowths from the head.

If, however, the description of these limbs is not essential to their definition, if it is extra information, the sentence must have "which," not "that," as the relative pronoun, and should read like this:

(b)	A bobbledoo has six limbs. The limbs, which are used for locomotion or grasping, are outgrowths from the trunk.

In sentence (a), there are limbs in addition to those used for locomotion or grasping. In sentence (b), there are ONLY those limbs used for locomotion or grasping.