The kanji 弟 primarily represents "younger brother". It denotes a male sibling who is younger than oneself. It focuses on the concept of age and the relationship between siblings, specifically from the perspective of the older sibling or the speaker.

・On-yomi (音読み): テイ (tei) ・Kun-yomi (訓読み): おとうと (otouto)

⚫︎ 弟弟はサッカーが好きです。 Translation: My younger brother likes soccer. ⚫︎ 兄弟弟と妹がいます。 Translation: I have a younger brother and a younger sister. ⚫︎ 弟さん、こんにちは。 Translation: Hello, [Mr./Ms.] younger brother. (Used respectfully)

The kanji 弟 is a 形声文字 (keisei moji), a phono-semantic compound. It combines the component 彐 (a hand, or a variant form) and the component 巿 (a brush or cloth). The original form of the character might have depicted a hand controlling or managing a cloth or brush. Over time, the meaning shifted to represent the younger sibling. The addition of the hand, potentially indicates the younger sibling is always next or below an older sibling.