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@@ -2,13 +2,64 @@
 
 This document acts as a Style Guide for the language and wording used in exercises.
 
-## General principle
+## Application
 
-All content should be written in US English.
+These rules should be followed in all exercises. 
+Existing descriptions and test-cases can be updated to adhere to them without requiring "replacement" test cases.
+
+### Consistency within an exercise.
+
+There are some terms that have multiple valid spellings (e.g. "lower case" vs "lowercase"). 
+Where a consistent style has not been agreed within this document, these must be consistent within an exercise.
+
+### Exceptions
+
+Exercises may vary from these rules if there is general consensus across maintainers that this is reasonable. 
+For example, an exercise about converting between different units might choose not to use SI measurements.
+
+## Language
+
+All content should be written in US English. In the future other translations may occur, but the "official" Exercism language is US English.
+
+### Measurements
 All units of measurement must be [SI](https://en.wikipedia.org/wiki/International_System_of_Units) or [SI-derived](https://en.wikipedia.org/wiki/SI_derived_unit) units.
-In the future other translations may occur, but the "official" Exercism language is US English.
 
-## Explain or substitute mathematical and esoteric terms.
+### Abbreviations, acronyms and initialisms
+
+Abbreviations, acronyms and initialisms are often more difficult to understand than other phrasing options, and can alienate people trying to learn.
+
+Many abbreviations are jargon. Avoid jargon where possible by using alternative language. Don't use abbreviations unless either:
+- The abbreviated term is better known than the unabbreviated term
+- The text will be excessively verbose without abbreviation
+
+When using abbreviations always explain what the term means on its first use. This will often, but not always, include expanding the abbreviation. It will rarely be sufficient to only expand the abbreviation.
+
+Here are some example rules:
+- Prefer "if I recall correctly" to "IIRC"
+- Prefer "as far as I know" to "AFAIK"
+- Prefer "queue" to "FIFO" and "stack" to "FILO"
+- Instead of describing an interface as "RESTful", describe it's specific properties
+- If you must use "CRUD", explain that it stands for Create, Read, Update, Delete and that these are the basic actions in standard databases
+
+An some examples of good usage:
+- "HyperText Markup Language (HTML) is the language used to describe document structure and content on the web" _(expanded and explained)_
+- "DNA, a set of chemical instructions that influence how our bodies are constructed" _(DNA is not expanded because "deoxyribonucleic acid" is unlikely to help explain what DNA is to our audience)_
+- "NASA, the United States' space agency, launched the Mariner 2 space probe in..." _(NASA is not expanded because the "National Aerospace and Space Administration" is much better known by its acronym than by its expanded name)_
+- "The Department of Motor Vehicles (DMV) is filled with sloths. That's why everything takes forever at the DMV" _(Define DMV the first time it is used)_
+
+#### Exceptions
+
+Some abbreviations are considered common, useful, and non-technical enough that we have decided to permit them:
+- `e.g.` or `eg`
+- `i.e.` or `ie`
+- `etc.` or `etc`
+- `docs`
+
+Contractions (e.g. "won't", "I'm", "that's") should be used sparingly if at all in exercise descriptions, but are not restricted in other language around the site (e.g. website copy, mentoring).
+
+## Choice of words
+
+### Mathematical and jargon terms.
 
 In any place that mathematical terms are used they should be explained or substituted out for terms that require less domain knowledge.