What is a two-letter language identifier called? [closed]

A list of languages might look like so:

  • English (en)
  • French (fr)
  • German (de)

What are the two-letter identifiers in brackets called?


Solution 1:

Specifically, these are ISO 639-1 Codes (from the International Organization for Standardization).

There is also a similar system but with three letters known as the ISO 639-2.