The Millennial generation is taking the workplace by storm. At more than 53.5 million people in the U.S. workforce, Millennials now outnumber Baby Boomers and Gen Xers. Not only that, but by 2025 Millennials will comprise about 75 percent of the workforce.

Despite their numbers, there are things many Millennials do that can actually hinder their careers and long-term success. If you're a Millennial, make sure you're not doing the following five things that can make you look really unprofessional at work.

1. Using Millennial lingo in professional settings.

While slang can seem appropriate among colleagues, or even in one-on-one interactions with your bosses, constantly using Millennial-centric slang in meetings or presentations is an indication you're still not ready for a true professional setting, and can even downplay how great your idea was in the first place.

2. Excessive punctuation and emojis.

Exclamation points are good when you want to make a message seem less harsh or more playful. Exclamation points are also an incredibly easy way to spot whether a person is fresh out of college or not. Millennials often feel that exclamation points are OK to use in abundance, when they should really be used sparingly. Also, make a point of laying off the use of emojis in your business correspondence--just say no!

3. Overly long emails.

Email messages can be a great tool for people to connect, contact one another, or simply stay up-to-date on a grand scale. However, emails that read more like penned essays are not as effective; they just reflect one's tendencies to prefer the electronic interaction to the face-to-face.

4. Frequently changing your mind.

While we all have the right to change our minds whenever we please, it's definitely a Millennial tendency to be aware of. When it appears you're unable to stick with or commit to anything, you look indecisive and wishy-washy. Limit your fickleness, and your professionalism will burgeon.

5. Constantly playing with your smartphone.

While we all love playing with our smartphones--sending texts and email messages, posting to Facebook, sending tweets, checking our Instagram accounts--Millennials love their smartphones more than most. And when all this love gets in the way of getting work done--or communicating with your co-workers--there's a problem. Limit your smartphone play time to lunch breaks or before or after work.