j (EN)

letter, symbol

letter “j”

1. the lowercase form of the letter "J"
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   The word "jet" starts with the letter "j".

symbol “j”

1. in mathematical notation in electronics, a symbol used to represent the square root of -1
   In electrical engineering, we use j instead of i to represent the square root of -1, so that it is not confused with current.
2. in mathematics, a symbol representing the second unit vector following "i"
   In a 3D coordinate system, the vector j points directly up along the y-axis.