* Defining "fluent" is subjective: What constitutes fluency? Is it perfect grammar, native-like pronunciation, a large vocabulary, or all of these things? Different organizations use different criteria.
* Data collection is difficult: Getting accurate language data for the entire world is challenging. Many countries don't have comprehensive surveys, and even when they do, the definition of "fluent" may vary.
* English as a second language: Many people learn English as a second or even third language, making it difficult to categorize their fluency.
Estimates and statistics:
* 1.5 billion: This is a common estimate for the number of people who speak English as a second language.
* 375 million: The number of native English speakers.
* Around 2 billion: This is an estimate of the number of people who have at least some level of English proficiency.
Overall: While we can't give a precise number, it's safe to say that English is the most widely spoken language in the world, and millions more learn it every year.