# Help:Definitions

## Introduction

Definitions are essential for the success of $\mathsf{Pr} \infty \mathsf{fWiki}$.

### Unambiguity above all

Everything used in the definition has to be linked to, so as to give a very precise definition.

### Multiple Definitions

Multiple definitions, generalizations of definitions and similar topics are discussed at Help:Multiple Definitions.

## What and what not to add

The general intent is to keep definition pages concise, placing as much as possible on other pages while maintaining a clear and unambiguous definition.

### Encyclopaedic descriptions

While informal definitions may be accepted in some exceptional cases, $\mathsf{Pr} \infty \mathsf{fWiki}$ is no place for expository blocks of text. If you've written something like this, you're invited to move the text to your User Page, personal sandbox or community sandbox. If you feel like there's a need for more coherence, you may be interested in setting up a properties page instead, or in enhancing the Also see section or Also defined as section if applicable.

### Well-definedness

It may happen that it is not self-evident that something is well-defined. In that case this has to be proved on a separate page, with a link in the Also see section.

## Types of definitions

Some types of definitions merit special attention because of their complexity.

### Nonconstructive definitions

Example: Tensor Product of Modules

### Definitions arising from a theorem

Example: Abscissa of Convergence