Ironically, unrequited love is the structural glue that sticks most of the characters in The Seagull together. Medvedenko loves Masha, but Masha loves Treplev. Treplev does not love Masha back, he loves Nina. Nina loves Treplev briefly but then falls madly in love with Trigorin. Arkadina loves Trigorin but loses his affections to Nina. Paulina loves Dorn though she is married to Shamrayev. Dorn sometimes shares an affection for Paulina, but his apathy for her appears to have begun before the play started and continues to fade during the course of the play. The couples and the unrequited lovers resonate and reflect off of one another, serving as parallels and mirrors of each other in the play. They represent different stages of life and of love. The clearest parallel involves Paulina and Masha. Masha's unrequited love for Treplev and decision to marry Medvedenko seems to mirror her mother's unhappy marriage to Shamrayev and her unrequited love for Dorn.
Masha, Sorin, Treplev, and Trigorin have existential crises in The Seagull. Masha hates her life and does not know why she goes on living a boring, unhappy life. She sniffs snuff and drinks heavily to hide from her pain and disappointment. Sorin encounters something of a mid-life crisis and an existential crisis though his life is more than half over. He questions what he did with his life and regrets his lack of attempting to meet his goals in youth. Treplev lacks direction in his life. He thinks he is talented and creative, possible of greatness, but does not have a precise goal in mind or point to make. He allows his ambition to overwhelm his ability. His loss of Nina's love, his failure at impressing his mother, and his life in the shadow of Trigorin's success eat away at his spirit and will to live.
Trigorin has an existential crisis when he becomes excited in the prospect of an affair with young Nina. Trigorin was not actively questioning his life or his life choices at the beginning of the play and seemed content. But Nina's interest in his work and in a relationship with him force him to think about his life and its present meaning. Nina represents a second chance at youth to Trigorin. He selfishly pleads with Arkadina to allow him to be with Nina so that he can relive his youth that was spent seriously writing, not frolicking with young girls. Trigorin wonders what he missed in life as a youth because of his writing and what else he missed. Nina's love for Trigorin opens his eyes and creates a new sense of awareness about himself that he had not experienced before meeting Nina. Once he recognizes his loss in the past, Trigorin cannot believe in a future that does not include the risk of a new experience. His life in the past loses meaning and his future threatens to only have meaning if he attempts to have an affair with Nina.
Chekhov emphasizes the mundane in life repeatedly throughout the play. This pattern of routine emphasizes the life-altering events that happen amidst ordinary experience and the ordinary experiences common to us all. Moments like going to dinner, playing cards, reading out loud, putting on a bandage, asking for a drink of water etc, continuously emphasize the everyday customs of being human and the uniqueness of moments that are not mundane but change our lives forever.