* Defining "language" is tricky: There's no clear consensus on what constitutes a distinct language versus a dialect.
* Constantly changing: Languages evolve, die out, and merge. New languages are created through pidginization and creolization.
* Limited data: Many languages, especially smaller ones, are not well documented.
Estimates range from 6,000 to 7,000 languages.
However, it's important to note that these are rough estimates and the real number could be higher or lower.