When to use Which, That, and Who

Writing Tips When to Use Which/That/Who

Proper use of which, that, and/or who shows attention to detail. Many people do misuse which/that, but if you use them incorrectly, many readers will notice and this will make you seem as if you are a careless writer.

For example:
When I formulated the business plan determined 20 percent of my grade I made sure to include a lot of statistics would appeal to the economics professor.

The first blank would be filled by "which" and set off by commas: the sentence makes sense and will not lose meaning even if the clause is removed:

When I formulated the business plan I made sure to include a lot of statistics that would appeal to the economics professor.

The second blank needs to be filled with "that" because the clause cannot be removed from the sentence without losing meaning.

The correct sentence is: When I formulated the business plan, which determined 20 percent of my grade, I made sure to include a lot of statistics that would appeal to the economics professor.

Use THAT when the clause is essential for the meaning of the sentence; do NOT set the clause off with commas.

Use WHICH when the clause is NOT necessary for the meaning of the sentence and always set off the clause with commas.

Use WHO when the clause refers to a person (regardless of whether the clause is essential to the meaning of the sentence or not).

The TRICKY thing with which/that (and why so many people get them confused) is they largely depend on what you, the writer, means. The same sentence can be grammatically and syntactically correct using either which or that. The correctness of use comes when you examine meaning.

For example:
The cap, which is on the table, is my most prized possession in the whole wide world. (The fact that the cap is my most prized possession is important; it doesn't matter WHERE the cap is; the fact that it is on the table is extraneous to the meaning of the sentence)
The cap that is on the table is my most prized possession in the whole wide world. (There are several caps in the room and I want you to know which one, specifically, is my most prized possession, therefore the location of the cap is possession, therefore the location of the cap is essential to the meaning of the sentence; notice: NO COMMAS)
OK, now you try:

I was at the Humane Society choosing a dog for my brother for Christmas. When I walked back to the cages, I knew immediately that the black lab (which/that) had the painted red toenails was the dog I had to have. (What if there was only one black lab at the Humane Society? Would it make a difference?)

A student (Kyle) is contesting a grade and spoke with the department chair regarding the official process. The department chair told Kyle he needs to follow the documented grade grievance policy, which/that is as follows: meet with me; if not satisfied, meet with her; if not satisfied, meet with the dean; if not satisfied, file a complaint to the judicial board.

My friends and I are uptown, enjoying a jazz concert in the park when a police officer approaches. He busts us for open container law ($75 ticket per person, FYI). We each had one beer that/which we had been nursing for the past hour.
Standard English is difficult to define beyond "the language that/which the dominant culture agrees is the standard."

By looking to the pedagogical approaches used in China, Israel, and the Arab world that/which teach China, Israel, and the Arab world that/which teach children the written form of a specific language, a model for educating our own children could also be created.

The teacher that/which taught me English thought she was a whirly-gig, whatever the hell that is.

ANSWER KEY:

that (if there are several black dogs); which (if there is only one black dog)

which (the clause is not needed; it is just more detailed information about the policy)

which (the fact that we had been nursing the beer for an hour is not significant to the meaning of the sentence)

that (you can't remove the phrase and still have the sentence make sense)

that (you need to know what sorts of pedagogical approaches you are looking at for the sentence to make sense)

who (never say that/which when talking about a person!) WHO: always use "who" when referring to a person (never which or that)