Final answer:
Iago is jealous of Cassio due to Othello's decision to promote Cassio over him and due to Iago's unfounded suspicions that his wife, Emilia, has been unfaithful with Cassio.
Step-by-step explanation:
The question pertains to Iago's motives for jealousy in Shakespeare's play Othello. Specifically, it seems to question why Iago harbors envy towards Cassio in relation to Emilia. The intricate dynamics of jealousy in Othello are manifested in Iago's complex character, who feels slighted by Othello for passing him over for a promotion in favor of Cassio. Additionally, Iago's machinations are also motivated by rumors and his own suspicions of infidelity involving his wife Emilia, whom he believes may have been unfaithful with both Othello and Cassio. This layered jealousy both is personal, stemming from Iago's own insecurities and imagined wrongs, and professional, due to Cassio's meteoric rise in military rank.