Britney Spears is one of pop music's defining voices. That's just a fact. When she emerged onto the scene in 1998 with "...Baby One More Time," the world hadn't seen a performer like her. Not since Madonna had a female artist affected the genre so profoundly.

Spears has continued to shock us throughout her 20+-year career, delivering live performances and fashion moments that people still reference today. She made a lasting impact on both the 2000s and 2010s, the latter which end in just a few weeks. The greatest embodiment of her legacy is, of course, her music. She's released nine studio albums—six reached number one on the Billboard 200—and on those records are some of the most influential pop songs of all time. There are also, naturally, some misfires. That's to be expected when you have a career as long and illustrious as Spears's. It comes with ebbs and flows, all of which have made her the iconic performer she is today.

Britney Spears's 10 best songs, below, represent the strongest elements of her artistry: catchiness, sensuality, and lyrics that are way smarter than people realize. As for her worst? Well, just listen to those. If anything, they make the genius songs all the more brilliant.

Best

10. "Born to Make You Happy"

Regressive lyrics aside, "Born to Make You Happy" is a euphoric slice of nineties bubblegum, featuring some of Spears's fullest vocals and one of her most memorable bridges. "Just call out my name, and I will be there. Just to show you how much I care," Spears sings, breathlessly, before a twinkly, energetic instrumental kicks in. It's lighter than air.

9. "How I Roll"

Rolling Stone named "How I Roll" the best pop song of 2011, and for good reason. It's the fifth track on Spears's album Femme Fatale, a fiery but standard collection of four-on-the-floor electro-pop. But there's nothing standard about "How I Roll." With highly-experimental production and playfully distorted vocals, it sounds like something Charli XCX or one of pop's other current tastemakers would release today.

8. "Overprotected"

Feeling overly controlled or scrutinized is a consistent theme in Spears's discography—just look at songs like "Piece of Me" or the music video for "Everytime" as proof. But this motif started with "Overprotected," the Max Martin and Rami-produced track that masks its introspection with a killer hook.

7. "Everytime"

This is, by far, Spears's most personal track. (She's credited as a songwriter alongside just one other person.) Believed by some to be an answer to Justin Timberlake's "Cry Me a River" video (which alluded that Spears was unfaithful in their early-aughts relationship), "Everytime" is a haunting, devastating exploration of regret and loneliness.

6. "Unusual You"

Perhaps Spears should swap "Everytime" for "Unusual You" the next time she performs a ballad. This melancholic, midtempo song is a favorite among Spears diehards. Hyper-electronic yet inexplicably warm, "Unusual You" shows Spears skeptical of a new lover who comes into her life. "Baby you're so unusual. Didn't anyone tell you, you're supposed to, break my heart? I expect you do, so why haven't you?," she sings, her voice drenched in Auto-Tune as subdued synths crackle in the background.

5. "Lucky"

Another song with a scrutiny theme—only this one is pure sugar. "Lucky" remains one of Spears's best early singles: a perfect blend of the sweet-pop sound from her first record and lyrics that feel just a little more grown-up. The song's bridge, bursting with melodramatic intensity, has become karaoke cannon for millennials.

4. "Gimme More"

Name three words more culturally potent than "It's Britney, bitch." You can't. "Gimme More" didn't exactly make the best first impression, as fans initially heard it during Spears's infamous performance at the 2007 VMAs. But it's since become a club anthem: grimy, relentless, and pulsating with hazy-3 A.M. debauchery.

3. "Breathe on Me"

Another deep-cut favorite among fans, "Breathe on Me" is the closest Spears has ever come to a Madonna Erotica era. This hypnotic piece of Euro-trance is sex personified, with a bridge that literally builds and explodes like an orgasm. As Spears said in a 2003 interview with Diane Sawyer, "Breathe on Me" is a song that puts you in the mood.

2. "Toxic"

Spears fans may roll their eyes at "Toxic" now, but it'd be foolish not to include it at the top of this list. After all, it's the only track that's earned Spears a Grammy (2005, Best Dance Recording) and its production, at the time, was revolutionary. "Toxic" is the most progressive song on Spears's In the Zone album, zipping with the techno-pop panache that defined radio in the 2010s. (This song, mind you, came out in 2003.)

1. "...Baby One More Time"

There's no way another song could've come out on top. "...Baby One More Time" is easily one of the most expertly-crafted pop tunes of all time. The first three seconds of the track aren't just well-known: they're part of our culture's very fabric. And the accompanying music video is just as impactful. "...Baby One More Time" definitively ushered in the Y2K pop era, and for that we are eternally grateful. It is Spears's best song based sheerly on the fact that it changed the course of popular music.

Worst

10. "E-Mail My Heart"

Neither this song nor the theme of it has aged well. All of Spears's early ballads are, admittedly, quite saccharine, but this one is just a bit too sincere.

9. "I Love Rock 'N' Roll"

Spears's music video for this Joan Jett cover is top-notch. But the song itself? It wasn't exactly necessary.

8. "My Baby"

The opening lyrics of this ballad, "tiny hands," have become a joke among Spears fans. She's talking about her children, which in theory should be sweet, but it comes off more comical than anything—especially when paired with the track's overly angelic production.

7. "Mmm Papi"

"Mmm Papi," Spears's attempt at sixties twang, falls flat due to its lackluster chorus. That being said, the singer gets creativity points for her deliciously camp vocal delivery.

6. "Big Fat Bass"

Vocal manipulation isn't necessarily a negative quality in Spears's music—not if it's used to creatively enhance a song. But that's not the case on "Big Fat Bass," which strips Spears of all personality and leaves her stranded in a sea of headache-inducing beats.

5. "It Should Be Easy" (feat. will.i.am)

That same note applies to "It Should Be Easy," which turns BritBrit into a robot and features an EDM breakdown that sounds dated upon delivery.

4. "Pretty Girls" (with Iggy Azalea)

"Pretty Girls" is, sadly, just a lukewarm attempt at recreating Ariana Grande and Iggy Azalea's song "Problem." Everything from the chanty, bratty chorus to Azalea's sleepy rap just feels off—and like a regression for Spears.

3. "Tik Tik Boom" (feat. T.I.)

"Tik Tik Boom" is catchy, sure, but Spears's voice is practically indiscernible in it, and the lyrics in T.I.'s verse are inexcusable. ("She like the way I eat her, beat her, beat her. Treat her like an animal, somebody call PETA." Um, excuse me?)

2. "Chillin' With You" (feat. Jamie Lynn)

It's nice that Spears featured her sister Jamie Lynn on "Chillin' With You," but the song itself is a bit underwhelming. Matchy-matchy lyrics and a head-scratching chorus are ultimately the cause of its downfall.

1. "Private Show"

Spears really stretched and played with her voice on her 2016 album, Glory. In some cases, like the song "What You Need," she triumphs, and on others, well...I'll let this track speak for itself. "Private Show," unfortunately, is an unlistenable song—and I say that with the upmost love and respect for Britney Jean Spears. This one should've been left on the cutting room floor.

Christopher Rosa is the staff entertainment writer at Glamour. Follow him on Twitter @chrisrosa92.

Originally Appeared on Glamour