This is a list of languages by total number of speakers.
It is difficult to define what constitutes a language as opposed to a dialect. Some languages, such as Chinese and Arabic, cover several mutually unintelligible varieties and are sometimes considered single languages and sometimes language families. Conversely, colloquial registers of Hindi and Urdu are almost completely mutually intelligible, and are sometimes classified as one language, Hindustani, instead of two separate languages. Such rankings should be used with caution, because it is not possible to devise a coherent set of linguistic criteria for distinguishing languages in a dialect continuum.
There is no single criterion for how much knowledge is sufficient to be counted as a second-language speaker. For example, English has about 370 million native speakers but, depending on the criterion chosen, can be said to have as many as 2 billion speakers.
There are also difficulties in obtaining reliable counts of speakers, which vary over time because of population change and language shift. In some areas, there is no reliable census data, the data is not current, or the census may not record languages spoken, or record them ambiguously. Sometimes speaker populations are exaggerated for political reasons, or speakers of minority languages may be under-reported in favor of a national language.