Tencho is a word meaning Tenno Dynasty, but its meaning shifted and came to be used for the Imperial Court, Japan itself, or rarely Tenno himself.
天朝（てんちょう）は天皇王朝をさす言葉だが、転じて朝廷、または日本国そのもの、もしくはまれに天皇をいう場合にも使う。