HTranslations.php

__($key, $domain = 'core') - Translate strings

_e($key, $domain = 'core') - Translate strings (echo them)

_m($key) - Translate string (flash messages)

_n($single_key, $plural_key, $count, $domain = 'core') - Retrieve the singular or plural translation of the string.

_mn($single_key, $plural_key, $count) - Retrieve the singular or plural translation