A patent specification is a unilateral statement by the patentee in words of his choosing addressed to those skilled in the art by which he informs them of what he claims to be the new features of the product or process for which the letters patent grants him a monopoly. It is those novel features only that he claims to be essential that constitute the pith and marrow of the claim. A patent specification should be given a purposive construction rather than a purely literal one which lawyers, by their training, are tempted to do by applying meticulous verbal analysis to it. (Catnic v. Hill, 1982, Lord Diplock)

The patentee must fully and particularly describe an invention and its operation so that those in the industry can carry it out without having to make further inventions. Patent specifications must be fair and must not be unnecessarily difficult to follow. If this is done, the description is considered sufficient. (Farbwerke Hoeschst v. Unichem Laboratories, AIR 1969 Bombay 255)

Types of Claims in Specifications:
Main claims: These are, as the name suggests, the main claims in a patent applications. These claims are generally made in the broadest possible terms.
Omnibus claims: These are claims as to arrangement which protect the applicant from infringement by the creation of alternative designs.
Subordinate claims: These are claims which include additional features.

Amendment
In an application to amend a patent specification, the patentee must fully disclose all relevant facts in the evidence filed in support of the application. (Chevron Research Co.’s Patent, 1970)
It is not relevant whether an amendment widens or narrows the monopoly claimed. The amended claim must relate to the same invention. (Edwards v. Acme Signs, 1990)