Post 4 in our series on localization skills for modern technical communicators
Most technical communicators encounter the phrase “write clearly” early in their careers and spend years refining what that means. Shorter sentences. Active voice. Consistent terminology. Plain language over jargon.
What fewer encounter is the idea that “write clearly” has a formalized, internationally recognized standard behind it, with 53 writing rules, a controlled vocabulary of approximately 900 approved words, and a history stretching back to the 1970s.
That standard is ASD-STE100 Simplified Technical English, known in the industry simply as STE, and in January 2025 it became an international standard for technical documentation.
If you work in aerospace, defense, or manufacturing, you may already know STE. If you don’t, this post is your introduction to a discipline that opens doors in some of the most demanding, best-paying sectors in technical communication.
Here’s my poem about Simplified Technical English to set the stage:
One word, one meaning; one rule at a time;
— CJ Walker herself
the clearest of manuals needs reason and rhyme.
Not simpler than simple, but sharper than plain:
STE supports safety, again and again.
What Is Controlled Language?
Before we get to STE specifically, it helps to understand the broader concept it belongs to. Controlled language is exactly what it sounds like: a version of a natural language (in this case, English) where the vocabulary and grammar are deliberately constrained.
That constraint is not about dumbing content down (and it’s not about haikus, either). The purpose of STE is to describe complex systems and complex tasks in a clear and simple form, so readers, even those with limited English proficiency, can understand the content easily. It is a precise and structured writing standard, not a simplified or low grade-level version of English.
This discipline serves two audiences simultaneously.
- It helps readers who are not native English speakers and who may be operating complex equipment in high-stakes environments.
- It supports translation. One of the primary objectives of STE is to make translation easier. If the approved words, their related meanings, and the types of sentence constructions in a text are controlled, variation in source texts is minimized, making it easier to translate text written in STE into the target language, whether by translators, neural machine translation engines, or large language models.
Both of these outcomes connect directly to what this strand is building. Controlled language is writing for translation taken to its logical conclusion: not just applying good habits, but systematizing them into a verifiable standard.
What Is ASD-STE100?
STE was created in the 1980s by the European aerospace industry under the former AECMA (now ASD) to improve the clarity of maintenance manuals in civil aviation. Over time, its use expanded into defense, rail, automotive, oil and gas, IT, medical devices, and many other safety-critical sectors.
The standard has two parts: rules for writing and a controlled dictionary.
The writing rules
The writing rules cover grammar, style, and sentence structure. The current edition consists of 53 writing rules and a dictionary of approximately 900 approved words.
The rules address things like sentence length (active voice preferred; sentences in procedures should be no more than 20 words), verb use (one approved meaning per verb; no synonyms), noun clusters (avoid stacking more than three nouns), and the use of pronouns (avoid where they create ambiguity).
The controlled dictionary
The controlled vocabulary lists approved words, each with a single approved meaning and a single approved part of speech.
When there are synonyms in English, STE selects one and does not include the others. For example, STE uses “start” instead of “begin,” “commence,” “initiate,” or “originate.” If a word is not in the dictionary, writers either avoid it or treat it as a technical term with a specific, defined meaning in their domain.
The January 2025 milestone – why it matters
ASD-STE100 Issue 9 introduces refined terminology, updated rules, and industry collaboration to enhance technical communication, marking a significant step in the evolution of STE.
While no new rules were introduced, 31 of the 53 existing rules were refined for improved clarity, and 555 entries in the dictionary were updated.
Most significantly, STE transitioned from a specification into an international standard. That change in status matters for technical communicators: it means STE is now more likely to be referenced in contracts, procurement requirements, and regulatory frameworks across a wider range of industries.
Why STE Matters for Localization
The connection between STE and localization is direct and well-established. Controlled source language reduces translation variability, which reduces translation cost and improves translation consistency.
STE does this by maximizing the efficiency of traditional translation tools and processes:
- Translation Memory (TM) Efficiency
When all writers use the same approved word for the same concept, translation memory works at maximum efficiency. - Improved Machine Translation (MT) Output
Predictable sentence structures help machine translation produce better output with less post-editing. - Increased Workflow Speed
Grammar constraints eliminate the ambiguous constructions that often cause translator queries, which increases workflow speed.
Standardized vocabulary reduces translation costs significantly, making controlled source language one of the highest-return investments for global documentation programs.
The AI Advantage: STE and Large Language Models
There is an increasingly relevant AI angle. The controlled language properties that make STE content easier for human translators to process also make it easier for large language models (LLMs) to process accurately.
- If the approved words, their related meanings, and sentence constructions are controlled, variation in source texts is minimized.
- This minimization makes it easier for neural machine translation engines and LLMs to handle the content.
- For organizations building AI-powered content systems, STE-compliant source content is a meaningful quality input.
STE Beyond Aerospace: Where It Applies Now
One of the most important things to understand about STE is that its origins in aviation maintenance documentation do not limit its current relevance. The standard was designed for any situation where complex technical content must be understood accurately, often by non-native English speakers, often in high-stakes environments.
The sectors where STE or STE-influenced controlled language is most actively in use or demand include:
- Aerospace and defense
Still the heartland of STE. Maintenance manuals, overhaul procedures, and technical orders for military and civil aircraft routinely require STE compliance. Primes and their supply chains specify it contractually. - Medical devices and life sciences
The FDA regulatory environment in the US, and equivalent frameworks in Europe and elsewhere, create strong incentives for consistent, unambiguous technical documentation. STE principles, even where not formally mandated, align with regulatory expectations for clarity and traceability. - Manufacturing and industrial equipment
Complex machinery with global installation and maintenance teams needs documentation that works for technicians across multiple languages and training backgrounds. STE provides the framework. - Rail and automotive
Both sectors have adopted STE-influenced approaches for safety-critical maintenance and operating documentation, particularly for products that are sold and operated across multiple markets. - Renewable energy
An emerging area: wind turbine maintenance documentation, solar installation guides, and grid infrastructure manuals are increasingly produced for global audiences with varied English proficiency.
For technical communicators who want to move into these sectors, being able to show solid STE knowledge is a genuine differentiator.
What STE Looks Like in Practice
The best way to understand STE is to see the transformation it creates. Here are three examples of the kind of rewriting STE demands.
Sentence length and structure
STE limits procedural sentences to approximately 20 words. Descriptive sentences may be slightly longer, but complexity is constrained throughout.
- Non-STE
“Prior to initiating the installation sequence, it is necessary to confirm that all power sources connected to the primary and secondary systems have been deactivated in accordance with the shutdown procedure outlined in Section 3.” - STE
“Before you start the installation, make sure that all power sources are off. Refer to Section 3 for the shutdown procedure.”
The meaning is identical. The STE version is easier to translate and leaves no room for misinterpretation about the sequence of actions.
One word, one meaning
STE controls synonyms. Where the dictionary approves “remove,” writers do not use “take out,” “detach,” “extract,” or “strip.”
Where the dictionary approves “close,” writers do not use “shut” or “seal” unless those are technical terms with specific definitions.
- Non-STE
“Detach the connector from the harness and extract the module from its housing.” - STE
“Disconnect the connector from the harness. Remove the module from its housing.”
This is significant for translation memory: every instance of the same action is expressed the same way, meaning every translation of that action can be reused without a new translation decision.
Active voice and direct instruction
STE strongly prefers active voice in procedural text, with the implied subject “you” for instructions.
- Non-STE
“The system should be restarted once the configuration has been saved.” - STE
“Save the configuration. Then restart the system.”
Clearer for any reader. Significantly easier to translate into languages where verb agreement and passive construction differ substantially from English.
How to Apply STE Principles Without Full Certification
Not every organization requires formal STE compliance, and not every technical communicator will work in a sector that mandates it. But the principles of STE are applicable and beneficial far beyond their formal domain.
If you work in sectors where STE is not required, you can still adopt a controlled-language mindset by:
- Building a team glossary and enforcing it
Choose one approved term for each concept and document it. This is the core of STE’s controlled vocabulary principle, and it applies everywhere, from software documentation to policy manuals. - Setting sentence length targets
Apply the 20-word guideline to procedural content and a 25 to 30-word guideline to descriptive content. Track compliance as part of editorial review. - Eliminating synonym variation
Audit your documentation for terms used interchangeably and standardize on a single preferred form. This is the most immediately impactful controlled-language change most teams can make. - Using a plain language framework
If full STE is not appropriate for your sector, plain language guidelines provide a structured alternative that shares STE’s core goals.
Many governments and regulatory bodies publish their own, including the US Plain Language Act requirements for federal agencies.
If your organization does operate in a sector where STE is mandated or preferred, the path to formal capability involves training, practice with the standard itself, and ideally exposure to an STE checker tool, several of which integrate with common authoring environments.
Issue 9 is available free of charge from the ASD-STE100 website.
Real-World Scenarios
These real-world case studies show how applying consistent, unambiguous technical content improves safety, streamlines regulatory reviews, and create significant cost savings in globally distributed operations.
The maintenance manual that grounded less
An aerospace maintenance organization implemented STE compliance across its fleet documentation after a series of maintenance errors were traced back to ambiguous procedural language.
Within two years, the rate of procedure-related maintenance queries from technicians in the field dropped measurably.
The change was not in the procedures themselves; it was in the precision with which they were written. Technical communicators who could demonstrate STE competency became essential to the program.
The medical device that cleared regulatory review faster
A medical device manufacturer preparing documentation for a multi-market launch adopted STE-influenced writing standards for its instructions for use.
Regulatory reviewers in three markets commented on the clarity and consistency of the documentation during the review process.
The launch documentation required fewer revision cycles than previous submissions. The technical communicator who had led the controlled language initiative was promoted to a documentation standards lead role.
The global industrial equipment rollout
A manufacturing company releasing a new industrial system across twelve markets found its previous documentation approach required significant per-market adaptation.
They needed to adapt for linguistic reasons and because source inconsistencies created problems that were solved differently by different translation teams.
Moving to controlled language for the next product generation reduced per-market adaptation time significantly and allowed translation memory leverage across the twelve language variants in a way that had not been possible before.
These real-world examples show how the precision and consistency of STE-influenced documentation directly translates into improved safety, efficiency, and also professional advancement for technical communicators who lead these initiatives.
Common Pitfalls and How to Avoid Them
Implementing STE or any controlled language initiative comes with specific challenges. Understanding these pitfalls, and how to proactively address them, is key to a successful implementation. I made a troubleshooting chart:
| Pitfall | What Goes Wrong | How to Avoid It |
|---|---|---|
| Treating STE as dumbing down | Resistance from writers who feel the standard constrains their craft | Frame controlled language as precision engineering, not simplification; the goal is clarity, not brevity for its own sake |
| Implementing vocabulary control without governance | Writers bypass the glossary; synonym variation returns | Assign ownership of the glossary; integrate it into authoring tools; make adherence a review criterion |
| Applying STE rules without understanding them | Writers follow the letter of the rules but not the intent, producing stilted prose | Read the standard itself (Issue 9 is free); take structured training; use an STE checker to learn from feedback |
| Assuming STE only applies in aerospace | Valuable controlled language opportunities in medical, manufacturing, and industrial sectors go unexplored | Assess any sector with complex procedures, global audiences, and high translation volume as a potential STE application |
| Starting with full compliance rather than incremental adoption | Teams are overwhelmed and the initiative stalls | Begin with the highest-impact rules: sentence length, one term per concept, active voice; add rules progressively |
| Neglecting the technical term dictionary | Writers do not know how to handle domain-specific vocabulary | Build and maintain a technical term dictionary alongside the general controlled vocabulary; STE explicitly supports this |
Career Opportunities
STE knowledge is a genuine differentiator in the technical communication job market. It opens access to sectors with higher documentation standards, higher compliance requirements, and correspondingly higher compensation for the technical communicators who can meet them.
- STE-Certified Technical Communicator
A number of training providers offer STE certification. While there is no single universally mandated certification body, demonstrating formal STE training and practical experience is a differentiator in aerospace, defense, and regulated manufacturing job applications. - Documentation Standards Lead
Organizations with large documentation estates and STE compliance requirements need someone to own the standard, train writers, manage the controlled vocabulary, and audit compliance. This is a senior individual contributor role that sits at the intersection of technical communication, governance, and quality management. - Controlled Language Specialist
A specialism that appears in job postings across aerospace, defense, medical devices, and large industrial organizations. Typically a step beyond general technical communication, commanding a premium on the base rate for equivalent experience. - Localization-Ready Content Architect
The technical communicator who can design source content architecture that is simultaneously STE-compliant, localization-ready, and AI-ready is genuinely rare. Organizations building global content pipelines are actively looking for this profile. - Regulatory Documentation Specialist
In life sciences, medical devices, and pharmaceutical manufacturing, the intersection of controlled language and regulatory compliance creates demand for technical communicators who understand both the writing standards and the regulatory frameworks they serve. This is one of the highest-compensating technical communication specialisms.
Industry demand is particularly strong in aerospace and defense, medical devices and life sciences, industrial manufacturing, rail and automotive, and renewable energy infrastructure. All of these sectors share the conditions that make controlled language essential: global audiences, safety-critical content, and high translation volume.
A Light Learning Path
Developing a practical understanding of STE doesn’t require a massive investment of time or money.
This light learning path is designed to be an accessible, incremental way for you to engage with the official standard, apply its core principles to your existing work, and build verifiable skills over the course of a few months.
- Weeks 1 to 2: Download the standard and read it
Issue 9 of ASD-STE100 is available free of charge from the ASD-STE100 website. You do not need to read it cover to cover; start with the writing rules section. Read the 53 rules and their explanations. Notice how many of them are formalizations of what you already know: sentence length, active voice, synonym control. - Weeks 3 to 4: Apply the core rules to a document you own
Take a piece of documentation you’ve written and audit it against the five highest-impact STE rules: sentence length in procedures, active voice, one term per concept, no noun stacking beyond three, and no ambiguous pronouns. Count how many instances you find. Rewrite them. The audit is the learning. - Month 2: Explore an STE checker
Several STE compliance tools offer free trials or free tiers, including HyperSTE and the TechScribe term checker. Running your revised document through a checker will surface patterns you missed manually and accelerate your understanding of how the rules interact. - Month 3: Keep applying your STE skills in new contexts
Stay tuned on this blog for more skills to move your forward and apply what you’re learning.
Your Next Career Move
STE is one of the few named, internationally recognized standards in technical communication. Knowing it by name is not enough; being able to apply it, demonstrate it, and articulate its business value sets you apart from the majority of technical communicators who have never engaged with it formally.
If you want to build the foundational technical communication competencies that STE builds on, our Fundamentals of Modern Technical Communication, Part 3 course by Ben Woelk and Jennifer Goode provides the context for managing and optimizing your modern technical communication practice, including content designed for international audiences. Find it here at the Firehead Training Academy.
For teams looking to make controlled language part of a broader content governance and AI-readiness strategy, The Clarity Lab is where Firehead’s expertise comes together. We work with organizations to structure your content assets for AI readiness and global scale, including controlled language assessments, localization preparation, and knowledge architecture.
If your organization is grappling with documentation quality across multiple markets, get in touch to talk about what’s possible: Firehead Consulting.
Firehead works with technical communicators at every stage of this journey; from those encountering STE for the first time to experienced practitioners moving into documentation standards and compliance roles.
- Explore all our courses at the Firehead Training Academy
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