Patent law is a legal system where a government grants to an inventor an exclusive right of stopping others from exploiting her invention in return of her full disclosure of the invention to the society. To acquire a patent, an inventor usually needs a patent specialist to help file or draft an application. Recently, "Patent English" has been considered a necessary skill of a patent specialist because it is one subject in the Taiwan patent bar exam. In fact, "Patent English" is still a developing concept in the field of English for Specific Purposes ("ESP"). In view of patent practice, "Patent English" is an English language skill necessarily for a patent specialist to communicate with foreign patent agents to help her local or foreign clients file a patent application. She also needs a skill to help her establish the knowledge about patent law, especially the American patent law. One approach is to read more court decisions to gain the knowledge. This paper intends to address a method of helping paten specialists learn the legal doctrines and applications explained in a court decision. Specifically, this article chooses a decision of the Supreme Court of the United States, Bilski v. Kappos, 561 U.S. 593 (2010), as an example to present what a complex decision is and how it can be analyzed. The Bilski decision is about the patent-eligibility issue related to business methods. This article has two parts. To begin with, a brief introduction of the American legal system will be presented. Regarding the Supreme Court, there are nine judges sitting there. In each case, a vote of five out of nine judges can form a majority opinion. In addition to a majority opinion, a Supreme Court decision contains a dissenting opinion, written by a judge who opposes to the majoritys view, and/or a concurring opinion, written by a judge who takes the same position with the majority but has a different reason or another reason. While legal doctrines are presented in the majority opinion of a court decision, the dissenting opinion or concurring opinion might help understand the concerns or intentions of the majority. Second, this article uses the Bilski decision to explain the structure of a court opinion and the interpretation of the courts opinions. Identifying the legal rules and reasons of judgment helps understand the law of patent. But, readers also need to understand the existence of ambiguity in each decision.