関連ワード:  is it easy to learn a third language    is it easier to learn a third language    is it hard to learn a third language    is it easy to learn a foreign language    is it hard to learn a foreign language    is it easier to learn a third language than a second    is it easier to learn a third language after a second    is it easier to learn a second or third language    why is it difficult to learn a foreign language    is it hard to learn 3 languages at once