• 宣言せんげん — declaration / proclamation
• 宣伝せんでん — publicity / propaganda
• 宣告せんこく — sentence / pronouncement
• 宣教せんきょう — mission / religious preaching
• 宣誓せんせい — oath / pledge

宣 is a 形声文字 (phonosemantic compound). The radical 宀 (“roof”) hints at a formal or authoritative setting. The phonetic part is 亘 (セン), supplying the sound. Together it suggests a message issued under authority — e.g., an official proclamation.

Common in words for official speech, announcements, broadcasting, and public statements.

政府せいふは 非常事態ひじょうじたいを 宣言せんげんした。
The government declared a state of emergency.

その企業きぎょうは 新あたらしい 製品せいひんを 宣伝せんでんしている。
The company is promoting its new product.