How Did 是 Come to Mean "To Be"? I have been looking into the etymology of the character 是.
The site Chinese Etymology notes that this character was: &quot;originally meaning straight or correct. The sun 旦 rises or 早 in the correct 正 place.&quot; It also notes that it is: &quot;from sun-day 日 rì and foot-complete 正 zhèng&quot;.
I am wondering how a character for &quot;straight&quot; or &quot;correct&quot; came to have the meaning of &quot;is or &quot;equals&quot;.
時期字體
字形
參考資料




西周金

虢季子白盤集成10173


春秋金

陳公叔父甗集成947


戰國・楚簡

4包山竹簡


戰國・楚簡

036信陽書簡


秦簡

24.28睡虎地秦簡


東漢隸

孔宙碑 


楷






「是」 (Baxter-Sagart OC: /*[d]eʔ/) is comprised of phonetic 「止」 (/*tə/), which is the lower component. The earliest meaning of 「是」 was this, later extended to mean to be.
The upper component's functionality is unknown, and was later corrupted to look like 「旦」. Note that 「旦」 or 「早」 in the corresponding time periods do not form part of 「是」, and so are unrelated to 「是」.