Season 1
Main article: Friends (season 1)
The first season introduces the six main characters: Rachel, Monica, Phoebe, Joey, Chandler, and Ross. Rachel arrives at Central Perk after running away from her wedding to her fiancé Barry and moves into her friend from high school's (Monica’s) apartment with her. Ross, who has had a crush on Rachel since the two of them were in high school, constantly attempts to tell her how he feels about her. However, many obstacles stand in his way, such as the fact that he is expecting a baby with his lesbian ex-wife, Carol. Joey is shown to be a bachelor and struggling actor, while Phoebe works as a masseuse and portrays a sort of "crazy" attribute to her personality based on her troubles as a child after her mother committed suicide. However the rest of the group loves her regardless. Chandler breaks up with girlfriend Janice (Maggie Wheeler), who frequently returns in later seasons. At the end of the season, Chandler accidentally reveals that Ross loves Rachel, who realizes that she feels the same way. The season ends with Rachel waiting at the airport for Ross’ arrival from a trip.

Season 2
Main article: Friends (season 2)
The second season begins with Rachel waiting at the gate for Ross to declare her love for him. However, she discovers that he is dating Julie (Lauren Tom), someone he knew from graduate school. Rachel's attempts to tell Ross she likes him mirror his failed attempts in the first season, although the characters eventually begin a relationship. Joey gets cast in a part in a fictional version of the soap opera Days of Our Lives, but his character is killed off after conflicts with the show's writers, claiming that he writes many of his own lines. Chandler gets back with Janice, his ex-girlfriend from season one. Monica begins dating Richard (Tom Selleck), a recently divorced family friend and 21 years her senior. In the season finale, they end their relationship when they realize that unlike Monica, Richard does not want children.

Season 3
Main article: Friends (season 3)
Season three takes on a significantly greater serialized format. Rachel begins working at Bloomingdale's, an upscale department store chain, and Ross becomes jealous of her colleague, Mark. Rachel decides to take a break; and Ross, hurt and drunk, sleeps with someone else, causing Rachel to break up with him. In the meantime, Chandler has a hard time dealing with their breakup because it reminds him of his parents' divorce. After believing she has no family except her twin sister Ursula (Lisa Kudrow), Phoebe becomes acquainted with her half-brother (Giovanni Ribisi) and birth mother (Teri Garr). Joey develops a relationship with his acting partner Kate (Dina Meyer), and Monica begins a relationship with millionaire Pete Becker (Jon Favreau) which ends because of disagreements between the two.

Season 4
Main article: Friends (season 4)
In the fourth season premiere, Ross and Rachel briefly reconcile after Ross pretends to read a long letter that Rachel wrote for him, but continues to insist that the two were on a break so they break up again. Joey dates Kathy (Paget Brewster), a girl that Chandler has a crush on. Kathy and Chandler later kiss, which causes drama between Chandler and Joey. Joey forgives Chandler only after he spends a day in a box as punishment. Phoebe becomes a surrogate mother for her brother and his wife Alice (Debra Jo Rupp). Monica and Rachel are forced to switch apartments with Joey and Chandler after losing a bet during a quiz game, but manage to switch back by bribing them with Knicks season tickets and a one-minute kiss (off-screen) between the girls. Ross begins dating an English woman named Emily (Helen Baxendale), and the season finale features their wedding in London. Chandler and Monica sleep together, and Rachel decides to attend Ross and Emily's wedding. While saying his vows, Ross uses the wrong name at the altar (Rachel's), to the shock of his bride and the guests.

Season 5
Main article: Friends (season 5)
Season five features Monica and Chandler trying to keep their new relationship a secret from their friends. Phoebe gives birth to triplets in the show's 100th episode. She gives birth to a boy, Frank Jr. Jr., and two girls: Leslie and Chandler. (They had originally thought that there were two boys and one girl, but decided to keep the name Chandler, despite the baby turning out a girl.) Emily states that the only condition in which she would remain married to Ross is if he stops all communication with Rachel. Ross agrees, but during a last dinner with all six main characters together, Emily phones Ross and, upon discovering Rachel is there, realizes she does not trust him, which ends the marriage. Phoebe begins a relationship with a police officer, Gary (Michael Rapaport), after finding his badge and using it as her own. Monica and Chandler go public with their relationship, to the surprise and happiness of their friends. They decide to get married on a trip to Las Vegas, but change their plans after witnessing Ross and Rachel drunkenly stumble out of the wedding chapel.

Season 6
Main article: Friends (season 6)
In the sixth season premiere, Ross and Rachel's marriage is established to be a drunken mistake. Ross and Rachel try to get an annulment because he doesn't want to have three divorces. However, he realized he couldn't do so and tried to keep their wedding a secret from Rachel. Nonetheless, they divorce several episodes later. Monica and Chandler move in together, causing Rachel to move in with Phoebe. Joey lands a role on a cable television series called Mac and C.H.E.E.S.E., where he stars alongside a robot. Ross gets a job lecturing at New York University and starts dating one of his students, Elizabeth (Alexandra Holden). The relationship ends because of their maturity differences. Phoebe and Rachel's apartment catches fire, and Rachel moves in with Joey, while Phoebe moves in with Chandler and Monica. Chandler proposes to Monica, who says yes even though her ex-boyfriend Richard confesses his love for her.

Season 7
Main article: Friends (season 7)
The seventh season mainly follows the various antics by Monica and Chandler, who begin to plan their wedding and run into financial problems which are quickly fixed by Chandler’s secret funds. Joey's television series Mac and C.H.E.E.S.E is cancelled, but he is offered his job back on Days of Our Lives. Phoebe's apartment is fixed, but is rebuilt with only one large bedroom instead of the original two, so Rachel decides to stay with Joey. The season ends during Monica and Chandler’s wedding where Phoebe and Rachel find a positive pregnancy test in the bathroom.

Season 8
Main article: Friends (season 8)
In the eighth season, it is revealed that the positive pregnancy test found at Monica's wedding belongs to Rachel. Phoebe at first tricks Rachel and tells her that the pregnancy test is negative, in order to achieve Rachel's real emotions on the realization of being pregnant. Rachel projects feelings of sadness when she thinks she's not pregnant, so Phoebe tells her the truth. The three of them rejoice in the bathroom. The season revolves around Rachel's pregnancy; Ross is revealed to be the father after an investigation involving a red sweater. Rachel and Ross decide to have the baby but do not resume their romantic relationship. Joey develops romantic feelings for Rachel, but she does not reciprocate them. Rachel gives birth to baby Emma in the season finale. At the hospital, Ross's mother offers him an engagement ring because she wants him to marry Rachel. Ross does not intend to ask Rachel to marry him, but he takes the ring anyway and puts it in his jacket pocket. Meanwhile, in the post-delivery room, Joey looks for some tissue for an upset Rachel, picks up Ross's jacket, and the ring falls to the floor. He kneels to pick it up and turns to Rachel, still on his knees and still holding the ring. Rachel accepts what she thinks is his proposal of marriage.

Season 9
Main article: Friends (season 9)
Season nine begins with Ross and Rachel living together as roommates with baby Emma. Monica and Chandler try to conceive a baby of their own but find out that they are unable to, due to health restrictions. Phoebe begins dating Mike Hannigan (Paul Rudd), and chooses to be with him over her ex-boyfriend David (Hank Azaria). Rachel and Emma move in with Joey in the middle of the season, and Rachel develops romantic feelings for him, while the rest of the "friends" try hard to get Ross and Rachel back together. The group travels to Barbados in the finale to hear Ross give a keynote speech at a paleontology conference. Joey and his girlfriend Charlie (Aisha Tyler) break up, and she begins a relationship with Ross. Joey and Rachel's feelings for each other return, and the finale ends with them kissing.

Season 10
Main article: Friends (season 10)
The tenth season closes several long-running storylines. Charlie breaks up with Ross to get back together with her ex-boyfriend. Joey and Rachel try to contend with Ross' feelings about them being together and decide it would be best to remain friends. Phoebe and Mike get married mid-season outside the Central Perk coffee house. Monica and Chandler apply to adopt a child and are chosen by Erica (Anna Faris). In the series finale, Erica gives birth to twins, to the surprise of Monica and Chandler — a boy, Jack (after Monica's father), and a girl, Erica (named after the birth mother). Monica and Chandler prepare to move to the suburbs, and Joey becomes upset with the changes in his life. Rachel gets fired from her job and accepts a new offer in Paris, but Ross, realizing he loves her, chases after her. Rachel realizes she loves him, too, and cancels her flight to Paris, agreeing to stay with him. The series ends with all the friends plus Monica and Chandler's new babies leaving the apartment, heading to Central Perk for a final cup of coffee. The finale dialogue used in this series is by Chandler, making a joke for the last time. The camera's last view is of all of the character's keys to the apartment on the counter table, finishing with a shot of the apartment door.