(in electrical engineering and electronics) the imaginary quantity equal to the square root of minus one.

1The tenth letter of the alphabet.

1. 1.1 Denoting the next after I (or H if I is omitted) in a set of items, categories, etc.

2"J"A shape like that of a capital J (without a crosspiece).

3archaic Used instead of I as the Roman numeral for one in final position.

1Jack (used in describing play in card games).

2Japan (international vehicle registration).

3Physics
Joule(s).

4(in titles) Journal (of)