Use the public helper functions

POM Translate helpers provide locale configuration, explicit translated values, registered strings, localized URLs, selectors, and JSON translation without direct storage access.

Call them after plugins are loaded and guard optional integrations with function_exists(). Most value helpers return the original source when a translation is unavailable. They do not escape for every possible output context.

Reference

Use full WordPress locale codes internally. Short language codes are accepted only by helpers that explicitly normalize requested locales.