Jisho

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Particle
1. strengthens a question, assertion, etc.Familiar language, See also かい, See also ぞい, See also だい, See also わい
Wikipedia definition
2. I (kana)い in hiragana or イ in katakana is one of the Japanese kana each of which represents one mora. い is based on the sōsho style of the kanji character 以, and イ is from the radical (left part) of the kanji character 伊. In the modern Japanese system of alphabetical order, it occupies the second position of the alphabet, between あ and う. Additionally, it is the first letter in Iroha, before ろ. Both represent the sound [i i].
Read “I (kana)” on English Wikipedia
Read “い” on Japanese Wikipedia
Read “I (kana)” on DBpedia

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