College Composition / Unit 7 CMP 0158 short lesson, about 20 seconds
Which and That
Captions available
The idea
In standard usage, which introduces nonessential clauses, with commas, and that introduces essential clauses, without them.
In practice
"The labs, which were built long ago, need updates" describes all the labs; "The labs that were built long ago need updates" picks out some.
Where people slip
If you can remove the clause without changing the meaning, use which and commas.
Your place on the trail
Every lesson rests on earlier ones and opens later ones. Tap any to jump.
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