Consider this example phrase:

Bob and Martha's dog

This could mean one of two things:

  1. (Bob) and (Martha's dog)
  2. (Bob and Martha)'s dog

How do I know which one is the right one, and how do I clarify that in my own writing?

  • 2
    "How do I know which one is the right one?" Usually, context. If you read "I saw Bob and Martha's dog trotting along with a steak in its mouth", it should be pretty obvious. Sometimes it's not so obvious, like "I just shot Bob and Martha's dog for stealing my steak." Context, context, context.
    – stangdon
    Commented Sep 14, 2016 at 23:39
  • 2
    To clarify the usage in your own writing, sometimes all you need is a comma: Bob, and Martha's dog. Sometimes you must be specific to avoid ambiguity: Bob's dog and Martha's dog. Commented Sep 15, 2016 at 0:27

2 Answers 2


The listener will assume the dog belongs to Bob and Martha, because that's the most common situation.

If you want to convey something else, you'll write something quite different, for example,

When I was on my walk this afternoon, I ran into our neighbor Bob. He was walking Martha's dog. I think he must be dog-sitting for her while she's out of town.

Short version:

I saw Bob walking Martha's dog.


When there's a need to show possession with compounded nouns, the apostrophe's placement depends on whether the nouns are acting separately or together.


Miguel's and Cecilia's new cars are in the parking lot.

This means that each of them has at least one new car and that their ownership is a separate matter.

Miguel and Cecilia's new cars are in the parking lot.

This means that Miguel and Cecilia share ownership of these cars. The possessive (indicated by 's) belongs to the entire phrase, not just to Cecilia.

Lewis and Clark's expectations were very much the same.

This tells us that the two gentlemen held one set of expectations in common.

Lewis's and Clark's expectations were altogether different.

This means that the expectations of the two men were different. Separate ownership is signified by writing both of the compounded proper nouns in the possessive form.

The source is here.

A brief footnote:

There may be situations where, even following these rules, without a context, you can't avoid a possible ambiguity this simply. A hilarious example was provided by @stangdon:

"I just shot Bob and Martha's dog for stealing my steak."

So sometimes, you have to think of an alternative, like "his and Martha's dog" or, as P.E.Dant suggested, "Bob, and Martha's dog", or introduce a bit of context— for example:

You know Bob and Martha—I just shot their dog for stealing my steak.

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