A number of sources have compiled lists of languages by their numbers of speakers. However, all such lists should be used with caution, for the following reasons.

• First, it is difficult to define exactly what constitutes a language as opposed to a dialect. For example, some languages, including CHINESE and ARABIC, are sometimes considered single languages and sometimes language families. Similarly, HINDI is sometimes considered to be a language, but together with URDU it also is often considered a single language, HINDUSTANI.
• Second, there is no single criterion for how much knowledge is sufficient to be counted as a second-language speaker. For example, ENGLISH has about 400 million native speakers but, depending on the criterion chosen, can be said to have as many as 2 billion speakers. 

  Entries identified by ETHNOLOGUE (https://en.wikipedia.org/wiki/Ethnologue) as macrolanguages are not included in this section (i.s.).