Infringement of a valid patent under Indian law is determined through a series of legal and factual questions that courts examine to assess whether the exclusive rights granted to a patentee have been violated. These questions arise primarily under the Patents Act, 1970, and judicial interpretation has refined their scope through various landmark decisions. The determination of infringement is not a mechanical exercise; rather, it involves a careful analysis of the patent claims, the allegedly infringing product or process, and the surrounding circumstances. The first and foremost question is: what is the scope and meaning of the patent claims? Patent claims define the boundaries of the invention and serve as the legal yardstick for determining infringement. Courts interpret claims purposively rather than literally, taking into account the description and drawings in the specification. The principle was emphasized in the case of Biswanath Prasad Radhey Shyam v. Hindustan Metal Industries, where the Supreme Court held that the claims must be construed in a manner that reflects the true nature of the invention. Thus, before determining infringement, the court must clearly understand what the patentee has actually claimed as the invention. The second question is: does the allegedly infringing product or process fall within the scope of the claims? This involves a comparison between the patented invention and the accused product or process. If all essential elements of a claim are present in the accused device, infringement is established. This is known as literal infringement. However, Indian courts also recognize the doctrine of equivalents to some extent, where minor variations that do not substantially change the function or result may still constitute infringement. In Ravi Kamal Bali v. Kala Tech, the Bombay High Court applied this principle and held that even if there are minor differences, infringement may