Definition of "j"

The tenth letter of the English alphabet, called jay and written in the Latin script.  examples

(slang) A term for a marijuana cigarette ('joint').

(mathematics) An alternative version of i, the positive square root of -1; used in the context of electronics.  examples

(mathematics) The second unit vector, after i  examples

(stenoscript) a suffix or final syllable /ʃən/ (-tion, -sion, etc.)  examples