* Defining "Language" vs. "Dialect" is subjective: There's no clear-cut line between a language and a dialect. It often depends on factors like mutual intelligibility, political considerations, and social factors.
* Continuous variation: Languages evolve and change constantly, leading to gradual shifts and variations. This makes it difficult to draw strict boundaries between different speech varieties.
* Under-documented languages: Many languages, especially those spoken by small, isolated communities, are not well documented or studied.
However, estimates vary greatly:
* Ethnologue: The most comprehensive resource, Ethnologue, lists over 7,100 languages.
* UNESCO Atlas of the World's Languages in Danger: This resource focuses on endangered languages and estimates around 2,500 languages are critically endangered.
Important note: These numbers only reflect the number of languages that have been identified. There are likely many more languages and dialects that remain undocumented and are spoken in small communities around the world.