src/Base/Model.php
public function t($category, $message, $params = [], $language = null)
    {
        if (!isset($language) && isset($this->app)) {
            $language = $this->app->language;
        }
        return isset($language)
            ? Reaction::t($category, $message, $params, $language)
            : Reaction::tp($category, $message, $params, $language);
    }
public function t($category, $message, $params = [], $language = null)
    {
        if (!isset($language) && isset($this->app)) {
            $language = $this->app->language;
        }
        return isset($language)
            ? Reaction::t($category, $message, $params, $language)
            : Reaction::tp($category, $message, $params, $language);
    }
Translates a message to the specified language.
Or returns a TranslationPromise for further translation

@param string $category Message category
@param string $message Message for translation
@param array  $params Parameters array
@param string $language Language translate to
@return string|Reaction\I18n\TranslationPromise