* No official list: There's no definitive, universally accepted list of English idioms.
* Continuously evolving: New idioms are constantly being created, and some become outdated over time.
* Regional variations: Idioms vary between countries, regions, and even social groups.
* Degrees of idiom-ness: There are borderline cases where it's debatable whether something is truly an idiom or just a figurative expression.
However, estimates suggest that there are tens of thousands, if not hundreds of thousands, of English idioms. Some sources even put the number in the millions, but that's likely an exaggeration.
Rather than focusing on the exact number, it's more useful to understand what makes an idiom an idiom and how to learn and use them effectively.