I have read some grammar points about adjective clauses, but I still have problems recognizing the right choice in questions requiring them.

A Jekyll and Hyde is a person who has two personalities, one of ---- is bad and the other good. (I guess it should be whom but the answer is which.)

And I wonder if using relative pronouns in this paragraph is correct:

He invents a drug that (which?) can separate them. When he takes the drug, he becomes an evil version of himself, whom (that?) he calls Mr.Hyde.

Can someone please provide information, or resources to get better answers?

  • 1
    For the first case, the answer is "which" because the reference is to the personalities, not the two names (which are really just part of a single name in this case) nor the "person". A generic, non-specific personality is a "what", not a "who". Jun 14, 2014 at 17:31

3 Answers 3


The relative pronoun who(m) refers to animate beings, like people or animals. Personalities, in the meaning it has in your example, means the characteristic traits of a person. A person's personality is not an animate being. You can't take it to the beach, for example, or feed it donuts. The personality of a person is an inanimate object (a thing). The relative pronoun which is used to represent inanimate things.

A defining relative clause gives us extra information which helps the listener to understand which things we are talking about:

  • The man who you saw yesterday is my best friend.

Here, who you saw yesterday tells us exactly which man we are talking about. A non-defining relative clause, on the other hand, gives us extra information about something or somebody we can already identify:

  • Your father, whom I've known for twenty years, is the most honest man I've ever met.

Here, the relative clause whom I've known for twenty years, is just giving the listener extra information. It is not helping the listener understand which of her fathers we are talking about!

The relative item that can be used for both things and people/animate beings. However it can only be used in defining relative clauses, and not non-defining ones:

  • Your father, that I've known for twenty years, is the most honest man I've ever met* [wrong]
  • The man that you saw yesterday is my best friend. [correct]
  • The sandwich that you bought looked very tasty. [correct]

That cannot occur after a preposition that has been moved to the front of the relative clause:

  • The man [of that you're talking] [wrong]

  • The table [at which you're sitting] is antique. [correct]

The options for your examples then are:

A Jekyll and Hyde is a person who has two pesonalities, one of which is bad and the other good.


He invents a drug which/that can separate them. When he takes the drug, he becomes an evil version of himself, who(m) he calls Mr. Hyde.

  • That would work fine for the last one, too, if you remove the comma as well: “He becomes an evil version of himself that he calls Mr. Hyde”. (Also, minor niggle: space missing between “Mr.” and “Hyde”.) Jun 14, 2014 at 19:42
  • @JanusBahsJacquet Yes, quite agree. But assuming the comma's not a typo, presumably it indicates a different intonational tune for the relative clause etc, different structure? I should probably edit the comma stipulation in, but right now am losing the will to die. Will have to do it in a bit ( - am writing mind-numbing reports right now). Thanks for the niggle! Jun 14, 2014 at 19:58
  • Thanks. I've read that if the clause is the noun,we can use that/which but if it is not identifying,we should use which. Here the clause is identifying the word "drug",maybe that's why we can use "that" but I don't know why it's preferable.
    – Hanna
    Jun 16, 2014 at 9:16
  • The other problem is sometimes it's not clear which clause is defining.
    – Hanna
    Jun 16, 2014 at 9:19
  • 1
    Thanks for visiting and helping out with English Student's post.
    – Mari-Lou A
    Jul 18, 2017 at 5:16

Hmm, found something that's got some relevance: http://www.dailywritingtips.com/when-to-use-that-which-and-who/

This fairly exactly calls out the first case above (using "which"), since the "personality" in question doesn't refer to a person, but to some thing a person has.

For the second text block, using "that" is probably more appropriate, though I don't think that the sentence is vague in meaning as some are when using "which". One should definitely use "whom" at the end, as the pronoun is a direct-object and refers to "himself", an obvious person.

  • Really thanks for that useful link...I don't understand why "which" is not appropriate or make the sentence vague?(When should I prefer "that"?)
    – Hanna
    Jun 14, 2014 at 17:49
  • Calling a personality a mere thing that a person has is a gross and dismissive oversimplification of a rather intricate metaphysical question, as is OP's source's pronouncement on which answer is correct. On that vs. which see this earlier question. And in Stevenson's classic horror story, the Jekyll personality is not presented as the good side of the human character with the bad removed, but rather the usual and normal mix of both. Jun 14, 2014 at 18:12
  • @BrianDonovan Whether it’s an oversimplification or not, a personality (in this sense) is certainly not animate enough to license who as its anaphor. Jun 14, 2014 at 19:47
  • @JanusBahsJacquet, I emphatically disagree. How familiar are you with Dissociative Identity Disorder, or the usages of those who deal with persons so afflicted? Pace Araucaria, alters can not only be fed donuts (as can my in-sink garbage-disposal unit, a most fitting destination for them) and taken to the beach (as can a towel), they can pass the Turing test. Jun 14, 2014 at 20:13
  • @BrianDonovan That is quite a narrow use case. I am not overly familiar with the field, but if referring to them as animate entities, I would never call them personalities. Alters, identities, personas—I don’t know what the most common term is, but personalities does not sound right to me. I would say that each alter/identity/persona have their own personality, but not that they are a personality. Jun 14, 2014 at 20:21
  • He invents a drug which can separate them.

This implies that you are speaking of only one drug. "Which" is used for non-restrictive or non-essential information, whereas "that" is used for restrictive or essential information. If you were to say "He invents a drug that can separate them," you are implying that he invented multiple drugs, but only THIS one can separate them. It distinguishes this drug from any other drug that might exist. Make sense?

  • When he takes the drug, he becomes an evil version of himself, whom he calls Mr.Hyde.

In this sentence, "HE" is the subject, "calls" is the verb, and "him" would be the object. "Whom" is in the objective case, and "who" is nominative. If you rephrase the sentence, "He calls HIM Mr. Hyde," then it becomes clear that you need "whom" (since "him" is an objective case pronoun).

  • While the latter half of your answer looks right, the first half seems wrong. Neither that nor which implies anything about single or multiple numbers of drugs existing. Jun 15, 2014 at 15:59
  • @jwpat7 Well, it actually does. Allow me to explain; If you say "The book THAT is on the table is mine," you are implying that there are some books elsewhere that are not yours since "that" is only used for restrictive clauses essential to the meaning of a sentence. Now, if you were to say "The book, WHICH is on the table, is mine," the fact that the book is on the table is no longer essential because you are now talking about only ONE book.
    – ncc-1701
    Jun 15, 2014 at 19:15
  • (a) "The book THAT is on the table is mine" does not imply that any other books exist, much less that some exist that are not mine. (b) "The book, WHICH is on the table, is mine" does not imply there's only one book on the table. For example, it could be a reply to a question that asks about a particular title from among multiple books and magazines on tables and chairs, where some magazines and books have identical titles Jun 15, 2014 at 20:14
  • .... (b) I'm not saying that there's only one book on the table. I'm saying that you use which to indicate nonrestrictive information. The fact that it's on the table is not essential (HENCE the commas offsetting the parenthetical statement). You are talking about THE BOOK that is yours. The one, single, solitary book that belongs to you, which happens to be on the table.
    – ncc-1701
    Jun 15, 2014 at 21:01
  • (a) On the other hand, "THAT IS ON THE TABLE" is a defining characteristic of the book. OK - technically, it's not saying that there are other books; however, the word "that" makes the fact that it's on the table ESSENTIAL to the sentence. It distinguishes it from any other book. And that is simply the difference between that and which in relation to restrictive/nonrestrictive clauses. That is all I am saying.
    – ncc-1701
    Jun 15, 2014 at 21:05

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