Few things in this world look as classically stylish as an oxford shirt.

This is probably the reason for oxford shirts' enduring popularity, going as far back as the time when women started wearing clothes that were "borrowed from the boys" -- the 1920s or thereabouts.

The best part about an oxford shirt is its versatility. It's always casual enough for a day at the beach but formal enough to wear with a pencil skirt. It's always demure enough for dinner with his parents but attractive enough that he will like it, too. A white or neutral-colored one can be worn year-round, with the heaviest or lightest fabrics.

It occurs to me that I've always put the oxford in roundups of "shirts you should be buying" but have never discussed it specifically. I believe it to be such a key ingredient in a women's wardrobe that this is a huge oversight on my part.

Of course, fit and colors do change slightly over the years. For a while, oxford shirts were fitted to the female shape, tapering in at the waist, then back out at the hips. In recent years, we've moved to "the boyfriend oxford."

Here are some tips for finding the best fit, and choosing updated colors and patterns:

FIT

Let's briefly discuss the term "boyfriend." I think this tag is often misconstrued as an excuse to run around in baggy, ill-fitting clothes. Boyfriend oxfords or boyfriend jeans should still be purchased in your actual size, and should achieve a relaxed look while still fitting some parts of your body.

This is what a proper boyfriend oxford does. It fits in the chest and shoulders, if casually, and is not tapered at the waist. It's not oversized, but it doesn't hug your curves.

I buy my oxford shirts in small/medium/large, but many stores carry them in numerical sizes if your shape usually requires the more precise sizing. The fit starts in the shoulders, which is particularly important with a collared shirt, but also pretty easy to figure out. The shoulder seams should match up with the ends of your shoulders; no tighter, no looser. The arms should be loose enough that you can comfortably roll up the cuffs and push them to your elbows.

Moving along to the chest, the biggest problem women have is gaping in at the third and fourth buttons. This totally jeapardizes the classic, casual and ladylike look of an oxford, so make sure this doesn't happen. Get as large a size as you need to eliminate this problem, then have the shirt tailored if necessary. (This is not a difficult tailoring job and should be inexpensive.)

It's OK for an oxford to be loose-fitting in the waist and hips. That's what makes it look effortless. It can be worn tucked or untucked, but make sure it's ironed.

COLORS

My inspiration for this column was the purchase of my new favorite shirt: a fitted boyfriend oxford with mint green stripes from Gap. I love oxford shirts for spring because you can dive into the hues of the season without having to freeze before the weather warms up. Try lavender, mint, pale yellow and pale pink.

You always want to keep one traditional blue oxford, and one in white. These are wardrobe staples, and you'll thank me next time you can't figure out what to wear.

For patterns, I stick to stripes and small Swiss dots. Anything else I tire of quickly, but if you want to test drive something splashier, go for it.

(E-mail Kristyn Schiavone at kristyn@simplestyleguide.com, or follow her on Twitter at @KKSchiavone.)

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