* Defining "language" is complex: There's no clear agreement on what constitutes a distinct language versus a dialect. Do mutually intelligible varieties count as separate languages?
* Continual evolution: Languages are constantly changing, evolving, and sometimes merging. New languages emerge, and older ones disappear.
* Data collection challenges: It's incredibly difficult to accurately document every language spoken in remote or isolated communities.
Estimates:
* Ethnologue: The most widely used resource, Ethnologue, currently lists over 7,100 languages.
* UNESCO: UNESCO estimates that over 2,500 languages are endangered.
Important to note: These are just estimates. The actual number is likely much higher, but it's impossible to know for sure.