These are the exclusions wording of my home insurance policy:

LPG fuelled, oil fired, warm air, solar and unvented heating systems or boilers with an output over 60Kw/hr

I have an “unvented heating system with an output of 40Kw/hr” and need to know whether it is covered or not.

The fact that the sentence contains an enumeration of items with commas could imply that the “and” is preceding the last item in the list “unvented heating systems or boilers both with an output over 60Kw/hr” meaning it IS NOT EXCLUDED however the “or” could also imply it is preceding the last item in the list “boilers with an output over 60Kw/hr” so the previous item would become “solar and all kinds of unvented heating systems” meaning it IS EXCLUDED.

Are there any specific rules in the English Grammar that can be applied to this kind of ambiguous sentences to resolve the ambiguity with 100% of certainty?

  • 3
    Couldn't you just ask your insurance company? Their answer would be far more authoritative than any you could get here.
    – alphabet
    Mar 24 at 2:43
  • 1
    Law SE is a better place to ask about legal language; normal English grammar does not always apply, and there are often rules for handling ambiguity.
    – Stuart F
    Mar 24 at 10:03
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    I'd read this as << Boilers with an output over 60Kw/hr and other heating systems with an output over 60Kw/hr, whether LPG fuelled, oil fired, warm air, solar, or unvented >> But (1) don't take this as authoritative, and (2) I don't see how 'vented' matches the other descriptors which list fuel types/energy sources. //// I'd certainly seek clarification. This screed violates Grice's maxim of manner (clarity). Mar 24 at 10:29
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    I would not enquire too deeply into the exclusions: at the moment, the ambiguity goes in your favour as a reasonable interpretation is that your boiler is not in the exclusions as it is under 60KwH. I refer you to the case of Oakhurt Dairy.(theguardian.com/books/2017/mar/16/…)
    – Greybeard
    Mar 24 at 11:08
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    If excluding certain boilers/heaters, I'm not going to give you a choice (or), but collect all those disallowed (and). If you're not sure if it's excluded, my lawyers already figured that out: it's excluded. Big heaters are unprotected by this coverage. Language unclear to you is not a negative to the insurer. Mar 24 at 15:42

1 Answer 1


In English grammar, this is known as syntactic or structural ambiguity. It occurs when a sentence or sequence of words has two or more possible meanings.

In your case, the ambiguity arises from the use of the conjunctions “and” and “or”, and the lack of clear punctuation to separate the items in the list. The intended meaning of a syntactically ambiguous phrase can generally—although not always—be determined by the context of its use. However, in this case, the context does not provide enough information to resolve the ambiguity with 100% certainty.

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