Your usage of the word their that is. As in my earlier post about minimum/maximum/criterion, their should be added to the endangered species list of the English vocabulary.
And here I am not talking about the very common confusion people have by using a word that sounds like the one they mean to use, but spells differently, and has a completely different meaning as in there, their, and they’re, i.e., I am not talking about homonyms; this should be the topic of a separate post.
No, here I am talking the substitution of the word their for its singular form your where grammatically the plural should be used. Let me give an example that often can be heard through intercoms:
Will the owners of a Minivan and an SUV with the following license plates please move your vehicle.
Note that in addition to the wrong possessive pronoun, also the singular form vehicle is used incorrectly. This sentence should read either
Will the owners of a Minivan and an SUV with the following license plates please move their vehicles.
If you are the owner of a Minivan or an SUV with the following license plates please move your vehicle.
When talking to people about this phenomenon, they usually agree but do not seem to think of it as a problem. What I ask myself is why people use your where they should use their? The only explanation I can come up with is that by saying your they think that the owner of that particular car might feel more personally addressed and might therefore be more inclined to move his/her car. But there is a simple solution. Simply use the second correct form from above. No need to use wrong grammar.
I personally cringe every time I hear such a sentence and wonder if I am the last person caring. Do you?