Consider that Alex is the son of Bob. Alex's mother (wife of Bob) is Caren and the grandmother of Alex (mother of Bob) is Deb.

Now Alex (son of Bob) killed Deb (mother of Bob), if I want to say that Bob's son killed Bob's mother [Alex killed his own grandmother], I would probably say (suppose I am telling this to someone who knows Alex, Bob, Caren and Deb and I don't need to repeat their original names)

His (Bob's) son killed his mother

This sentence sounds very ambiguous to me. It can have two interpretations:

  1. His son (Bob's son) killed Caren (Bob's wife)
  2. His son killed Deb (Bob's mother)

Is my original sentence ambiguous? How do I remove this ambiguity from the sentence?

  • I find your explanation of the various relationships incredibly confusing, but so far as I can make out, A killed his paternal grandmother D (there's not necessarily any reason to explicitly mention A's parents - father B and mother C). – FumbleFingers Oct 29 '20 at 14:14
  • The sentence is meaningless and should be deleted. – TaW Oct 30 '20 at 13:35
  • You don't have to use pronouns. – JonathanZ supports MonicaC Oct 30 '20 at 15:10

The ambiguity in "his son killed his mother" comes from who each use of 'his' refers to.

There are any number of ways you could remove the ambiguity, but the two most obvious to me that keep broadly the same sentence structure are:

  1. Whatever comes after the word "killed" defines who was killed by the son, so make that more specfic:

"His son killed his own paternal grandmother"

  1. Re-order the sentence so that each use of "his" can only refer to the same person (it cannot refer to the grandmother as she is a woman):

His mother was killed by his son.

  • 1
    "grandmother" is ambiguous because there are 2 grandmothers. – DavePhD Oct 30 '20 at 0:57
  • Not only is DavePhD correct - "grandmother" is ambiguous because there are two but also - "His mother was killed by his son…" takes you right back to the same problem… just with slightly different wording. Could you Post an outline of what you'd like to describe or, if this is generic, take it to your tutor, being prepared for several hours of detailed discussion? – Robbie Goodwin Oct 30 '20 at 1:55
  • Thank you Astralbee. Very enlightening answer! – Sphinx Oct 30 '20 at 10:06

It is ambiguous.

By far the simplest way to remove the ambiguity is to use names

A killed D.

There are other ways but all require more thought to work out, they might depend (for example) on working out that "his" can't refer to D because D is female. But this requires thinking and logic. If you don't want to be ambiguous, just use names.


I think the most typical way to resolve this is with the word own:

His (B's) son killed his own mother

This means whoever is currently "his" (B) killed that person's (B's) mother and isn't ambiguous.

If we don't know who is referred to by his, you need to use a name.

  • 2
    I'm not a native speaker, but I think this is still ambiguous (to the point that your sentence misleads me into thinking that the person who was killed is A's mother, not B's mother). Also, compare your sentence ("His son killed his own mother") with Astralbee's ("His son killed his own grandmother"). They should mean the same. – Fabio says Reinstate Monica Oct 29 '20 at 23:24
  • @FabiosaysReinstateMonica Why should they mean the same? The whole premise of this question is that the original sentence is ambiguous. So both interpretations could be correct. In my opinion, adding "own" is a valid way to resolve the issue of ambiguity. We have no way of knowing if the boy's mother or grandmother is killed, though. – Kakturus Oct 30 '20 at 8:26
  • 3
    While I agree that adding "own" makes it unambiguous, I disagree on what that unambiguous meaning is. To me, it is quite clear that "his son killed his own mother" means that the son killed the son's own mother. Since you disagree, this is apparently still ambiguous after all (despite both of us considering it unambiguous). – Dave Sherohman Oct 30 '20 at 11:48
  • Own should be unambiguous but doesn't seem fluid to me...I still have to sit and think about it for a minute. Also, "his own son killed his mother" should have the second meaning, but likewise doesn't seem fluid to me. – user3067860 Oct 30 '20 at 12:43

One solution: His mother was killed by his son. Compare with "His mother was killed by her son".

But the ambiguity is only removed due to different gender. What if his father was killed by his son? Back to square one.

Another classic example is "He is walking his dog". Compare that to "He is walking his dog". Intonation hints that it is someone else's dog, but writing cannot reflect that well. Here, 'own' can be used but only for the common use. Which is not the one you want to highlight. You can say "He is walking his own dog", but not "He is walking him over there's dog".

English grammar lacks the pronomen of [his own], and simply uses "his" for all occasions, so ambiguity needs to be sorted out by context.

This becomes even more obvious for the cases where the english language does have support.

"I am walking my dog" "I am walking your dog"

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