Do you ever get confused about the difference between that and which, and the correct usage of these words? I do. Maybe not so much confused as distracted, forgetful. It’s one of those things we should have had down cold before matriculating to middle school, but which drifts from focus with time. So today, we focus thereupon it.  

There are many such things in our language. I hear otherwise articulate people say things like, “Bob and me got up early and went fishing.” English ain’t easy.

A. Small dogs, which often bark, should get extra treats.

B. Small dogs that often bark should get extra treats.

C. Meetings, which occur on Wednesday, are held in Room #6.

D. Meetings that occur on Wednesday are held in Room #6.

See the difference? All four of these sentences are grammatically correct. But their meanings are different.

I guess reasonable people could arm wrestle over the comma usage, but not today.  

A & C add information about their subjects, small dogs and meetings. (You might not otherwise know that small dogs often bark or that meetings are on Wednesday, but you need to.) B & D limit the information.

In A, all small dogs often bark and should get extra treats. In B, only small dogs that often bark get extra treats; others don’t, and don’t get extras.

In C, all meetings are on Wednesday and always in Room #6. In D, Wednesday meetings are in Room #6; meetings on other days might be someplace else.

So the trick is to make note of sentences which add information, as opposed to those that don’t.

And who knew that Windows Live Writer had graphical smiley faces? Cool.