The language state when referring to locked languages. File core/lib/Drupal/Core/Language/LanguageInterface

Language written right to left. Possible value of $language->direction. File core/lib/Drupal/Core

The language code used when no language is explicitly assigned (yet). Should be used when language information is not available or cannot be

public LanguageInterface::getId() Gets

Special system language code (only applicable to UI language). Refers to the language used in Drupal and module/theme source code. Drupal uses

The type of language used to define the content language. File core/lib/Drupal/Core/Language/LanguageInterface

Language code referring to the default language of data, e.g. of an entity. See the BCP 47 syntax for defining private language tags:

public LanguageInterface::getWeight()

Defines a language. Hierarchy interface \Drupal\Core\Language\

public LanguageInterface::isDefault()