• 陛下へいか — His/Her Majesty
• 登陛とうへい — audience with the emperor (formal)
• 天皇陛下てんのうへいか — His Majesty the Emperor
• 皇后陛下こうごうへいか — Her Majesty the Empress

The left radical ⻖ (こざとへん) often relates to land or structures. 陛 originally referred to stairways in palaces — symbolizing a rise to meet authority. Today, it’s almost exclusively seen in honorifics for royalty, especially in the phrase 陛下.

天皇てんのう陛下が 登場とうじょうされました。
His Majesty the Emperor has appeared.

陛下へいかに 謁見えっけんする。
To be granted an audience with His Majesty.