In the ever-changing modern office, dress code is the one thing that has remained largely ambiguous. And while other office guidelines for decorum, employer/employee relations and punctuality are typically clearly laid out, the ever-elusive “office dress code” usually isn’t.

So before you go buy a dozen t-shirts or a suit in the name of “smart casual,” you might be curious – what does it actually look like for the office?

TheStreet asked experts what practically dressing “smart casual” is for men and women.

What Is Smart Casual?

Smart casual is a dress code that is typically comprised of well-fitting, neat and appropriate pieces that are slightly less formal than a business casual or business professional dress code. However, smart casual is much more elevated and put-together than dressing for off-hours and avoids items that are too casual or loose-fitting.

Getting its origins as far back as the 1920s, the term “smart casual” has evolved over the decades to its most common connotations today.

But, how do experts define “smart casual”?

According to Dave Arnold, President of Arnold Partners, LLC and executive recruiter for the tech industry, dressing “smart casual” is much more about elevating typically casual looks.

“Smart casual is employing finer-quality clothes that are still casual but well-fitted, in-style and of good fabrics. Smart casual does not imply flashy or flamboyant,” Arnold told TheStreet. “Take a look in the mirror before you leave the house and smile. This should never be construed as arrogance or trying to out-dress your peers. It is a matter of looking sharp and in-style. As a recruiter I look for people who have self-confidence and self-awareness – how they dress and how they carry themselves is part of this.”

In fact, Arnold claims that, as a recruiter, dressing smart casual as a default for interviews can be essential to getting the gig – and eventually getting promotions as well.

“For interviews it is tricky. You need to learn the culture of the company before your interview. If possible, go a day before and watch people come and go from the building to get a sense of the dress code, or find a contact on LinkedIn who works there and ask them,” Arnold advises. “Dress one level above your interviewer. Have your spouse, roommate, best friend, personal shopper approve your outfit.”

But apart from the recruiter perspective, stylists have their own definition of smart casual.

For Diane Lloyde Roth, who has dressed CEOs and celebrities alike as the owner of the luxury boutique L’Armoire in New Canaan, Conn., smart casual is much more about making sure you are focusing on how your clothes fit and if the individual pieces look put-together.

“This is not the time to use a cheap blouse or T-shirt that is wrinkled and does not fit correctly,” Roth says. “You are supposed to look smart but casual, not like you just finished a workout or pulled your clothes out of the hamper! Smart casual is perfect for an outing with business associates, especially during the daytime when you will be out of the office or not in a formal environment.”

The transitional nature of smart casual – from the office to an event or lunch meeting – seems to be a major aspect when picking out your daily ensemble, according to these experts. Will Noguchi, head stylist at Bombfell, claims as much. The men’s stylist has worked with the likes of Ralph Lauren, (RL – Get Report) Covergirl, Harper’s Bazaar Greece, Vogue Portugal, Vogue Arabia and more – and certainly knows a thing or two about styling customers for the office.

“The idea behind smart casual is to dress ‘smart’ by looking professional while also being approachable and ready for any occasion,” Noguchi told TheStreet. “My smart casual mantra is ‘elevated basics.’ When shopping, look for well-fitting items in solid colors that are a step above your casual wear. Items with elevated trims, buttons, and finishing details help dress up your look and allow your basics to be more office appropriate.”

The Importance of Dressing Well

But apart from looking nicer, multiple studies have shown that dressing more professionally (as with a smart casual dress standard) can actually lead to more CEO-like qualities.

A study done by Yale in 2014 used a sampling of 128 men between the ages of 18 and 32 to participate in mock negotiations. The sampling was split into three groups – one that dressed “poorly,” another that dressed neutrally and one that dressed professionally. While the groups dressed poorly and neutrally amassed hypothetical profits of $680,000 and $1.58 million respectively, the participants who dressed professionally generated a hypothetical average profit of $2.1 million. And while the study certainly doesn’t take every situation into account when dressing nicely for work, there are dozens of other studies that point to other benefits of dressing well – including promotions and raises.

A 2015 study by the Social Psychological and Personality Science journal concluded that people who dressed more professionally had better big-picture-making skills and exhibited higher levels of abstract thinking. The study was performed on 361 participants in five different sub-studies.

But apart from stronger big-picture thinking, dressing better may actually correspond to promotions in the workplace.

In fact, a recent survey by OfficeTeam concluded that 86% of professionals and 80% of managers claimed that clothing choices affected someone’s chances of being promoted.

As a tech recruiter, Arnold claims as much.

“Dressing well everyday once you have your new job is also important. Well dressed people are generally more confident and perceived to be well organized,” Arnold added. “Dressing smart casual will lead to faster promotions and a stronger reputation in the workplace. It just needs to be done with a dollop of class and not be over the top.”

So, how do you actually dress smart casual?

How to Dress Smart Casual

Much like the style itself, dressing smart casual seems to have shifting parameters depending on the particular office. Still, TheStreet got some helpful tips from experts for a variety of work environments and personal styles.

Consistent throughout their tips, stylists and recruiters generally concluded that dressing “smart casual” is more about pieces that are elevated from what you might typically wear. For example, several stylists suggested taking basics like tailored dresses or pants and paring them with nice but more casual pieces.

Smart Casual for Women

Women generally have more of a range when dressing for work. And with so many more options than their male counterparts, it can be that much more confusing when determining what “smart casual” actually looks like (especially when office guidelines are ambiguous).

Stephanie Naznitsky, executive director for OfficeTeam, claims that you might not even have to change your wardrobe too much if you already have business-appropriate staples.

“You may be able to mix and match elements from formal and casual dress codes and add certain accessories to show your personality. For example, a tailored cotton casual dress with a formal blazer could be considered smart casual,” Naznitsky wrote in a note.

But for women, what kinds of things are good for smart casual?

Elements of Smart Casual

For the most part, a rotation of dresses, blazers, cardigans, tailored pants, heels and khakis are generally appropriate. But the main thing experts stressed was not to try to be too flashy or trendy, and to instead focus on accessorizing or using unique design elements to dress up a regular, well-fitted outfit.

“Smart casual is more about the ability to mix pieces in a polished way than about the actual pieces themselves. For example, a blazer works for both smart casual and business casual,” Maria Turkel, a stylist and former TV wardrobe supervisor told TheStreet. “Wearing a blazer in a smart casual way is more about the ability to create outfits using color, pattern and texture.”

When she isn’t helping dress clients at Fortune 500 companies or start-up CEOs, Turkel, as a wardrobe supervisor for the classic TV show “Friends,” helped dress the likes of Jennifer Aniston and David Schwimmer – and claims the experience helped her get an idea of what “smart casual” was