Considering the different parts of a patent application, the most important part is the claims. The statue that relates to the format of the claims is 35 USC section 112 and more specifically, the second paragraph. This paragraph sets forth a requirement to 'particularly point out and clearly claim the invention'. The only acceptable way to 'particularly point out and clearly claim' an invention in a statutory classes as defined by 35 USC section 112 is by means of a English sentence. This restriction may be the source of many problems in claim drafting because of problems of writing in English and in the meanings of words.
The standard custom with respect to sentence construction in claim drafting is that each claim should be the direct object of a single sentence. The length of the sentence does not matter. To start with, the sentence may begin with 'I (or we) claim' or the equivalent 'What is claimed is'.
The standard patent office practice is also to insure that each claim begins with a capital letter and with a number. So that each claim may read as a complete sentence when taken with the introductory phrase such as 'I claim'. Exception for standard abbreviations such as the colon and semicolon, no other periods are permitted in the body of that claim.
As a result of the single sentence rule, grammar especially verb forms should be watched carefully.
I claim: a pen enterprises
This does not form a complete sentence.
I claim: a pen comprising
This does not violate the complete sentence rule.
In conclusion, the claim should form a complete sentence by forming the direct object of the phrase 'I claim'. Begin each claim with a capital letter and a number.
Furthermore, it is acceptable to include more than one claim in utility patents. Namely, 35 USC section 112 provides that the specification shall include with one or more claims.
In design patent applications, only one claim is permitted.
Further, any utility patent application with only one claim, that claim should not be numbered.
When there is more than one claim, each claim must start with an Arabic numeral. The claims must be numbered consecutively, and to follow good practice, the claims should be grouped and numbered in a logical order for consideration by the examiner which will be assigned to the patent application. The usual practice is to begin with the broadest claim and proceed to the narrowest claim and to group similar types of claim together.
Certain practitioners may try to slip a broad independent claim among the pending claims claiming that the examiner will not notice and hoping that the examiner will allow all the claims grouped together.
This is not a recommended practice.
A claim usually has a preamble and body.
Most claims have a preamble which may be an introductory statement having a purpose to name or define the thing which is being claimed. Preambles may be quite long or may be quite short depending on the type of claim that is being used.
The preamble for most claims should be simply a general definition of the invention to be claimed. The length and the detail should be chosen to match the body of the claim.
The set of writing the preamble should not have been taken up until the scope of the claim is determined. Unnecessary and limiting limitations or statements anywhere in the claims should be avoided and this warning is applicable to the preamble.