1. In the literal sense of a "postscript" (P.S.) in a letter:
* Preamble: This would be something you put at the *beginning* of a letter, introducing the main topic.
* Introduction: Similar to a preamble, this would set the stage for the main content.
* Foreword: This is often used in books to provide context or background information.
2. In the sense of an "afterthought" or "addendum":
* Precedent: This is something that comes *before* and sets a precedent for what follows.
* Prologue: This is a section that comes *before* the main story in a book or play, often giving background information.
* Foreword: Again, a foreword can set the stage for the main content, coming before it.
3. In the sense of a "postscript" as a computer file format:
* Other file formats: There are many other file formats for documents, images, and other data. Some examples include PDF, DOCX, JPG, PNG, etc.
* Source code: If the postscript file is a representation of a program, the opposite could be the source code that produced it.
4. In a more abstract sense:
* Beginning: This is the opposite of the end, which is what a postscript often marks.
* Introduction: This sets the stage for the main content, while a postscript often comes after the main content.
To give you the most appropriate opposite, I need more context about how you're using the term "postscript."