* "Understanding" is subjective: What constitutes "understanding" a dialect? Is it being able to understand every word, most of the words, the general meaning, or just recognizing it as a distinct accent?
* Dialect boundaries are fuzzy: Dialects often blend into one another, making it difficult to draw clear lines.
* Geographic variation: Understanding varies by region. A dialect widely understood in one part of the world might be less understood in another.
However, we can make some educated guesses:
* Standard dialects of major languages: Standard dialects like Standard American English, Standard British English, or Standard Mandarin are often taught in schools and used in media, making them more widely understood.
* Dialects with large speaker populations: Dialects spoken by large numbers of people, like Hindi in India or Spanish in Latin America, are likely to have a larger understanding base.
Ultimately, "most widely understood" depends heavily on the context and definition of understanding.