i
UK: aɪ | US: aɪ
n. the 9th letter of the English alphabet
n. (mathematics) the imaginary unit (√-1)
pron. first-person singular pronoun (subjective case)
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The word "I" traces back to Old English "ic," derived from Proto-Germanic "*ek," and ultimately from Proto-Indo-European "*éǵh₂." Its spelling simplified over time (e.g., Middle English "ich" → "I"), retaining only the vowel sound. As a pronoun, it reflects the universal linguistic focus on brevity for high-frequency words. The mathematical use ("√-1") was introduced by Leonhard Euler in 1777, repurposing the letter to avoid confusion with other symbols.
I am learning English etymology.
In algebra, "i" represents an imaginary number.
She said, "I will call you later."
The word "I" is the shortest complete sentence.
Euler standardized "i" for √-1 in complex equations.