Amendment

The process of adapting the text of a specification for a patent application (or, sometimes, a granted patent) to address objections that have been raised by the Patent Office (or other parties). 

There are strict rules that apply to the amendment of a patent application once it has been filed.  In particular, it is not possible to add anything that wasn't already present in the application as filed.  This is the main reason why drafting is such a critical stage in a patent's life, because it sets the boundaries for what can (and can't) be done later on if issues arise. 

It should be noted that there are additional requirements that apply to amendments of a patent after it has been granted.  Specifically, it is a common requirement of many patent systems (including the UK and Europe) that a patent cannot be amended to extend the scope of protection it provides.  That is to say, a granted patent cannot be amended to cover anything that wasn't already covered by the patent as originally granted.  This is to provide certainty to third parties that a granted patent can't be altered in a way that covers their activities (unless those activities were already covered by the patent as granted). 

Occasionally, these two requirements interact in a way that proves catastrophic for a granted patent during opposition or invalidity proceedings.  This situation is commonly referred to as "the inescapable trap".  It occurs when the claims of a granted patent were amended during prosecution to include subject-matter that wasn't contained in the patent application as originally filed, but where removal of that subject-matter from the claim would extend the scope of protection provided.  In such cases, it is not possible to remedy the situation (as at least one of the requirements will be violated), and the patent will be revoked.  It is therefore necessary to take great care when amending a patent application to avoid such issues from arising later on.

Related Terms: Added Subject-Matter; Drafting; Prosecution; and Revocation.