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Taylor Swift is one of those celebrities so famous that even if you don't listen to her music, you probably know something about her. Usually, the assumption is, "Isn't she the one who always writes songs about her boyfriends?"

It's true that Swift, 27, launched her career in 2006 as a teenager with "Tim McGraw," a wistful ballad about a guy she dated in high school. When she became a star, she paired off with other stars and wrote about them: Joe Jonas, John Mayer, Jake Gyllenhaal.

While she rarely names the subject of song, she leaves hints via coded messages in the album's liner notes, leading to a media frenzy every time she releases new music — and will likely continue the practice when she drops her sixth studio album, "Reputation," on Friday.

But those who know Swift only from those headlines and her big commercial hits ("Love Story," "You Belong With Me," "We Are Never Ever Getting Back Together") miss the fact that her music goes far beyond crushes and exes. Swift, who has written or co-written every song she's ever recorded, also tackles substantive subjects.

We took a dive into Swift's albums to track her evolution on various themes:

Life lessons

Album: "Taylor Swift" (2006)

As the story goes, aspiring teenage singer-songwriter Taylor Swift knocked on doors around Music Row, dropping off demo CDs. Her parents eventually saw enough promise to move from Wyomissing, Pa., to Nashville, where Swift became the youngest songwriter ever signed to Sony/ATV Music Publishing, at age 14.

Shortly afterward, Swift landed a record deal with Big Machine. As she was suddenly thrown into an adult world, her songwriting was still very much from a high schooler's perspective.

"I don't know what I want, so don't ask me," she sang on "A Place in This World" (Swift, Robert Ellis Orrall, Angelo Petraglia). "Cause I'm still trying to figure it out."

Her lyrics veered from extreme confidence to self-doubt: "I'll be strong, I'll be wrong, oh, but life goes on — I'm just a girl trying to find a place in this world." She also assured her listeners: "I'm not the only one who feels the way I do."

Album: "Fearless" (2008)

Swift's solo-written "Change," an anthem about not giving up, was chosen as a 2008 Summer Olympics theme song — but "Fifteen" was the standout track from the Grammys' album of the year, convincing critics that Swift was a true force. (Rolling Stone dubbed her a "songwriting savant.")

In the song, also a solo write, Swift took on the role of the older and wiser teen: She knew what it was like walking through the school hallways, terrified to make eye contact with anyone but also hoping the cute senior noticed you. She told the cautionary tale of her best friend, Abigail, who "gave everything she had to a boy who changed his mind — and we both cried."

Album: "Speak Now" (2010)

Swift wrote this entire album herself. While the quiet "Innocent" got many headlines — it chided Kanye West for interrupting her acceptance speech at the 2009 MTV Music Video Awards — one overlooked song was "Never Grow Up," a melancholy guitar acoustic tucked between Swift's forays into rock and pure pop. In the track, 20-year-old Swift grappled with the fear and loss that arrives during the early years of adulthood.

Swift addressed her words to a newborn baby. "Take pictures in your mind of your childhood room, memorize what it sounded like when your dad gets home," she sang, adding, "I just realized everything I have is someday gonna be gone."

Album: "1989" (2014)

"Welcome to New York" (Swift, Ryan Tedder) kicked off Swift's official pop era — the album's opening track was bursting with glee at all the excitement the Big Apple had to offer: "Welcome to New York — it's been waiting for you!" Swift had only just recently purchased a $20 million penthouse in Tribeca, so she earned some mockery when she was then named New York City's "global welcome ambassador."

But the pop star didn't care as she reveled in the freedom of the city. "Everybody here was someone else before," Swift sang. "And you can want who you want, boys and boys and girls and girls."

Friendship

Album: "Taylor Swift" (2006)

As obsessed as Swift would eventually become with her powerful "squad," a BFF group made up of models, singers and actresses, she frequently talked about how she was bullied and ostracized in middle school. On "The Outside," which she wrote by herself as a teenager, you could feel her pain: "How can I ever try to be better? Nobody ever lets me in. I can still see you, this ain't the best view, on the outside looking in."

The sad track was bookended by the buoyant "I'm Only Me When I'm With You" (Swift, Orrall, Petraglia), accompanied by a music video that showed Swift goofing around with her bandmates and best friend, Abigail. While the lyrics allude to romantic soul mates ("I don't try to hide my tears, my secrets or my deepest fears, through it all nobody gets me like you do") Swift's fans have adopted it as an ode to friendship.

Album: "Fearless" (2008)

A similar phenomenon occurred on "Breathe," co-written with singer-songwriter Colbie Caillat. Listeners could easily assume it's about a boyfriend ("You're the only thing I know like the back of my hand, and I can't breathe without you, but I have to") but Swift confirmed it's actually about the end of a close friendship.

Album: "Red" (2012)

Swift's most famous — and happiest — friendship song arrived in the form of "22" (Swift, Max Martin, Shellback), an upbeat track that basked in a carefree existence, dancing and making fun of your exes and eating breakfast at midnight after a night out: "We're happy, free, confused and lonely at the same time, it's miserable and magical, oh yeah!"

The song's hidden clue on the album liner notes was "ASHLEY DIANNA CLAIRE SELENA," also known as her close pals Ashley Avignone, Dianna Agron, Claire Kislinger and Selena Gomez.

Fame

Album: "Red" (2012)

By her fourth album, Swift was officially an international celebrity. She also started to collaborate with Swedish maestros Max Martin and Shellback, who helped shape her new pop sound.

But "The Lucky One," which she wrote by herself, was a bit of a return to form. Like a country song, it told a story — a starlet accomplishes her dream, and then realizes that the perks ("big black cars and Riviera views") might not outweigh the dark side of fame ("your secrets end up splashed on the news front page.")

"They tell you that you're lucky, but you're so confused, cause you don't feel pretty, you just feel used," Swift sang.

Album: "1989" (2014)

Swift's stardom skyrocketed again as her pop songs took on mass appeal. "Blank Space" (Swift, Martin, Shellback) is a parody of the tabloid media's characterization of Swift: A needy serial dater with a long list of ex-lovers who can tell you she's insane. And someone who, when she gets dumped, "goes to her evil lair and writes songs about it for revenge," as Swift once put it. Swift started writing the lyrics as a joke, and then realized the character was actually fascinating — as the song goes, "a nightmare dressed as a daydream."

Martin and Shellback also co-wrote "Shake It Off," one of Swift's top-selling singles, that hit back at her critics who were "gonna hate, hate, hate, hate, hate." In a YouTube interview, Swift said she wanted to write a "joyful" song about the criticism she gets on a daily basis — otherwise she would just burn with resentment forever.

Revenge

Album: "Speak Now" (2010)

Swift first displayed her thirst for vengeance against exes on songs like "Picture to Burn" (Swift, Liz Rose) on her first album, and "Better Than Revenge," about a romantic rival, which she wrote for "Speak Now." But on that third album, her motivation also went beyond boyfriends with "Mean." The song's rumored genesis was a critical blog post by music writer Bob Lefsetz, who roasted Swift's cringeworthy duet with Stevie Nicks at the 2010 Grammys.

In return, Swift painted her critic as an eventual bitter, washed-up loser, "drunk and grumbling on about how I can't sing." Swift concluded, "All you are is mean — and a liar and pathetic and alone in life."

Album: "1989" (2014)

Swift's most infamous revenge track is "Bad Blood" (Swift, Martin, Shellback). Once she revealed that the tune was about a fellow female pop star who tried to "sabotage" an arena tour, the internet quickly figured out that it was Katy Perry, who hired several backup dancers away from Swift's Red Tour.

Although it might seem like a benign slight, Swift's lyrics were rough: "Did you have to hit me where I'm weak, baby, I couldn't breathe, and rub it in so deep? Salt in the wound like you're laughing right at me."

Album: "Reputation" (2017)

After her longest break without releasing new music, Swift dropped "Look What You Made Me Do" in August. She and collaborator Jack Antonoff shared writing credits with Fred Fairbrass, Richard Fairbrass and Rob Manzoli, the trio behind "I'm Too Sexy," because Swift and Antonoff interpolated the 1990s hit.

The dance-pop track declared that the "old Taylor" is "dead." Still, she leaned heavily on her tried-and-true revenge theme, clearly aimed at her nemeses Kanye West and Kim Kardashian West, with whom she has been feuding for years. "The world moves on, another day, another drama, drama," Swift chanted. "But not for me, not for me — all I think about is karma."