"Button-down" is the most misused word in men's clothing. A button-down, you know, is a men's dress or "business" shirt which has collars that are each secured down to the front panel of the shirt by… a button! Shocking, I know. But we have become confused however with the button-front shirt, which nearly all men's office-type shirts are, as they have buttons as well, just down the front, not at the collar-tips, and also the popular phrase, "button-down culture, " which technically means a culture of uniformity. (And when I say "dress shirt, " I do not mean the shirt intended for use in formal evening wear, or what we would call black tie—what is also popularly referred to as the "tuxedo, " which, please don't say tuxedo. I mean shirts that are not t-shirts, basically, my dudes.) So now that we are all very clear on what a button-down shirt is, we can talk about when it is acceptable for a man to wear it.

It's important to remember that the button-down was a very informal shirt when it was invented around 110 years ago! (To people like me, who did not have many adult businessmen around me growing up, I had no sense of the formality or lack of such in men's fashion, and so context helps.) Over time, it has become more formal than, say, the t-shirt, which only evolved into being shortly before the button-down, but was until recently pretty much considered "underwear."

And yet, still some important trappings of its informality remain. This is more true on the Eastern seaboard than in California, so these guidelines skew east. (As all things should!) Although I do understand in Los Angeles that you may literally dress in animal pelts and legwarmers to the office, and I've made my peace with that.

In general, in grown-up land, there are some pretty firm guidelines.

You may wear a button-down…

• On Fridays, with khakis.

• On your own free time, whilst running errands, etc.

• On a casual date.

• With a knit tie and perhaps a tie bar, in sort of an ironically nerdy way.

• Under a casual sweater.

• When you want to look somewhat preppy when out for fun, in summer, that kind of thing. (Ironically or not.)

• To go uptown to get stationery engraved. (I just said that to annoy you, really, and also to make sure I could still spell "stationery.")

— When you work in a very casual office, with no real dress code, where perhaps people wear t-shirts or sweatshirts to work, like, say for instance you work at 36 Cooper Square.

• When you are David Beckham.

You may not wear a button-down…

• With a suit—almost never ever. (This rule may be broken a bit by women? That's complicated though! And in a few specialty cases, that probably don't apply to you! So err on the side of safety and don't do it.)

• Coatless, in an office where ties are standard for men (and forward-thinking women).

• At a job interview.

Source: www.theawl.com