j / jay are similar-sounding terms with different meanings (referred to as homophones). To better understand the differences, see below for definitions, pronunciation guides, and example sentences using each term. 👇
j: (noun) the 10th letter of the Roman alphabet.
jay: (noun) United States diplomat and jurist who negotiated peace treaties with Britain and served as the first chief justice of the United States Supreme Court (1745-1829). (noun) crested largely blue bird.
j: jh·EY
jay: jh·EY
(Examples are Wikipedia snippets under the CC ShareAlike 3.0 license. Definitions drawn from WordNet.)