Even well-written claims are very hard to understand. Adding poor grammar to the mix makes claims painful to read and possibly more vulnerable to invalidity arguments in litigation.
Let's start with a couple of questions...
Is a patent claim a sentence?
Nope. It looks like a sentence. After all, it starts with a capital letter and ends with a period. But there is one important thing missing. A patent claim does not ever have a verb.
So what is a patent claim?
Each patent claim is a REALLY long noun. The noun is something like a method, system, or a non-transitory, computer-readable medium. All of the words that come after the noun just provide details of that noun.
1. A cake comprising:
flour;
sugar;
eggs; and
baking powder.
The noun of this claim is a cake. Everything else tells us more about the cake. If only more claims were this tasty.
What about the word "comprising"? It looks like verb, but here it functions as an adjective. If you want more details, "comprising" is the start of a participle phrase that functions as an adjective that modifies the noun "cake".
A single verb in a true sentence will not end in "ing". For example, "Jeff eating donut" is not a sentence. You could say "Jeff is eating a donut" but now we have the additional verb "is" to make it a sentence.
Let's look at another patent claim:
1. A method comprising:
mixing cake ingredients;
baking the cake ingredients; and
eating the cake ingredients.
The words "mixing", "baking" and "eating" also look like verbs, but here they function as nouns. Each of these words is a gerund that starts a noun phrase. Each of the limitations in this claim is a noun phrase.
Let's look at one last patent claim:
1. A cake comprising:
flour, wherein the flour is sifted;
...
Here, the word "is" is truly a verb, and the phrase "the flour is sifted" could be a complete sentence. In the claim, however, the phrase is a relative clause that acts as an adjective to tell us more about the flour. The claim outside of that clause still does not have a verb, and the claim is still just a noun.
In summary, a claim is just a noun, albeit a really long noun. Please keep that in mind when writing your claims!