Merriam-Webster defines it two ways: English used in business, with an emphasis on correctness and the conventions of business correspondence, and English taught in non-English-speaking countries in courses built for commercial fluency within a limited vocabulary. In practice, it's short, direct English for meetings, emails, and negotiations. Think use instead of utilize, no idioms, and mostly simple tenses (past, present, future simple, plus present perfect and present continuous).

A controlled written language, officially ASD-STE100, developed in the early 1980s to help non-native speakers understand technical manuals without ambiguity. It's mandatory in aviation and defense, with strict rules: no phrasal verbs, three tenses only, roughly 20-word sentences, and articles used even where you'd normally drop them. Text written in STE typically shrinks by about 20% and is far easier to skim.

Here's the problem: there's no official definition. Some schools sell it as a vocabulary list for your profession. Others, like my friend Dr. Rachel Wulff, teach it to native English-speaking researchers preparing scientific papers for publication, a completely different skill from what a non-native engineer needs on an international project. Same label, genuinely different things depending on who's teaching it.

All three, and none of them taught in isolation. What actually helps is a teacher who's lived the overlap: someone who can spot which of the three you're missing in which moment and teach them as one connected skill instead of three separate courses. That's the whole premise behind English for Engineers.