Some English adjectives that begin with the letter J are "jealous," "jovial," "jaunty," "jazzy" and "judicious." Other adjectives that begin with J are "jaded," "jittery," "jinxed" and "jingoistic."
"Jealous" describes a resentment or anger over the success or achievements of someone else. English speakers occasionally use the adjective as well to describe someone who is overly watchful in guarding something, usually in the context of a romantic relationship.
"Jovial" describes someone who displays joy, playfulness and good humor. "Jaunty" describes someone with fashion and style. This adjective can also apply to a lighthearted and lively action or personality.
"Judicious" applies to someone who displays good judgment or wisdom. "Jaded" describes someone who is wary, usually as a result of experience. "Jittery" describes someone who is very nervous, tense or uneasy. "Jinxed" describes something that carries bad luck or misfortune. "Jingoistic" describes someone with a nationalist or patriotic attitude, especially in the context of war.
Another adjective that begins with J is "jagged." This adjective applies to something with notches or teeth along its edge, like a knife. "Jewish," another adjective beginning with J, can describe a person who practices Judaism or something associated with the Jews. "Jubilant" is an adjective that describes someone who displays joy or satisfaction, usually upon triumph.