Because the claims of each patent application define its subject matter, are searched and examined before a patent can issue, and ultimately give rise to the specific legal rights held by the owner of the patent, the claims are a very important part of each patent application.

Assuming that the results of the Professional Patentability Search were hopeful, given appropriate time and budget, a skilled patent attorney can typically draft claims that have a reasonable likelihood of eventually receiving a favorable reaction from the patent examiner, and therefore will be issued in a patent.

If special care is taken in the search and drafting process, these issued claims have a good chance of being upheld if challenged via litigation. Because poorly-drafted claims can be refused by the examiner as unpatentable, or can result in an issued patent being held not infringed or even invalid, claim drafting should be left to a skilled patent attorney.

Such a skilled patent attorney will typically draft claims of several different types, and of varying scope. Typically, the professional will draft claims for devices, systems, compositions, and/or methods.  In certain technology areas ("arts"), additional claim types are sometimes presented.  For example, in the software realm, claims have been drafted for unique data structures, user interfaces, and waveforms.  For biotechnology, claims for vaccines, assays, and diagnostic kits are common.

Claims are classified as independent or dependent.  Independent claims refer to no other claim. Dependent claims refer to another claim and further limit its subject matter.  Patent applications contain at least one independent claim, and typically many dependent claims.

Often, the claims will contain what appears to be arcane language and a run-on structure, which are traditional and expected by examiners.