Looking at examples like Basic English or Simple English, I see phrases like "controlled language" or "controlled vocabulary". Is there a simpler word?
with their different nuances, are the simplest terms that capture exactly what you are asking about.
Basic English is a selection, a simple subset of English for easy learning, intended to allow good communication early in the learning process.
World English is an attempt to label the common subset of English as spoken around the world by educated non-native speakers.
But there is no single word that captures such a subset. It seems almost impossible to have one given that what you are asking for is a qualification of English.
If you ever listen to English-speaking expats abroad, the ones that are good communicators intentionally use very simple words with often hilariously simplified grammar. That's
: a simplified speech used for communication between people with different languages
Specifically, it's pidgin English.
When people grow up speaking pidgin, it becomes a