preamble

The formal introductory clause of a patent claim. Depending on the circumstances, the preamble may or may not define a narrowing element of the claim. The preamble usually only defines the setting or context in which the elements of the claim appear. As a Jepson claim preamble sets forth the setting of the new invention, the use of Jepson format results in an implied admission that what is recited in the preamble is known in the prior art.