* Defining a "language" is tricky: Is a dialect a language? What about creoles or pidgins? Where do you draw the line between languages and regional variations?
* Constant change: Languages evolve, merge, and disappear. New languages emerge, and some become extinct.
* Lack of comprehensive data: It's difficult to gather data on all languages, especially in remote or under-documented areas.
Estimates:
* Ethnologue, a widely cited source, lists around 7,151 languages.
* Other sources give estimates ranging from 6,500 to 9,000.
It's important to note that these are just estimates, and the actual number is likely to be somewhere within that range.