The kanji 定 generally conveys the idea of "to determine," "to decide," "to fix," "to establish," or "to settle." It implies a state of being firm, stable, and unchanging. It can also refer to something that is regular, fixed, or scheduled. The meaning revolves around the concept of making something definite and certain.

・On-yomi (音読み): テイ (tei) ・Kun-yomi (訓読み): さだ（める） (sada(meru) - to decide, to determine, to fix), さだ（まる） (sada(maru) - to be decided, to be settled)

⚫︎ 決定 (kettei) Translation: Decision; Determination. ⚫︎ 定期 (teiki) Translation: Regular; Fixed term; Periodical. ⚫︎ 予定 (yotei) Translation: Plan; Schedule; Arrangement.

The kanji 定 is a phono-semantic compound (形声文字; keisei moji). The radical is 宀 (うかんむり; ukanmuri), which means "roof" or "house," indicating a covered space or a place. The phonetic component is 正 (sei), meaning "correct" or "upright." The original meaning of 定 might have related to fixing a position or setting something in a fixed place within a house, implying establishing something and making it firm and stable. Over time, the meaning expanded to encompass the broader concept of determining and deciding.