Many inventors that write their own patent applications use the term “consists of” instead of the preferred term”comprises”. For example, if their invention is a new mixture, they may write “my invention consists of A, B, and C”. To the Patent Office, these words (consists of vs. comprises) have very different meanings. While this wording choice can have dire consequences in the claims of a Non-Provisional application, it can also have consequences if used in the specification of provisional and Non-Provisional applications.
The phrase “consisting of” is closed-ended and excludes any element, step, or ingredient not specifically mentioned after that phrase. Unfortunately, if an inventor that says that their invention or some element of their invention “consists of X, Y, and Z, then they have said to the Patent Office that their invention only includes elements X, Y, and Z.
However, the term “comprising”, which is synonymous with “including,” “containing,” or “characterized by,” is inclusive or open-ended and does not exclude additional, unrecited elements or method steps. If an inventor says that their invention or some element of their invention “comprises X, Y, and Z, then they have said to the Patent Office that their invention can have other elements in addition to X, Y, and Z. For example, their invention could include A, B, and/or C as long as it also has X, Y, and Z.
To get the greatest protection when describing your invention, it is best to avoid using the term consist and instead use comprise or comprises. For example, the mixture comprises A, B, and C.