One option I've seen used is a table something like:
CREATE TABLE strings(id INT, lang TEXT, string TEXT);
INSERT INTO strings VALUES (1, 'en', 'Hello World');
INSERT INTO strings VALUES (1, 'es', 'Hola Mundo');
INSERT INTO strings VALUES (2, 'en', 'Header');
INSERT INTO strings VALUES (2, 'es', 'El encabezamiento');
It has the advantage of being fairly easy to add new languages or words and phrases without needing to change schemas.