What a woman wears on any given day is the result of a quick calculation involving many variables: Is it raining? Does she have a date after work? Is her underwear label showing? But, more powerfully, it's the result of millions of years of evolution.

That's where you come in. Evolution is all about sexual selection-and for women, at least, choosing a mate begins with choosing how we display ourselves. As you may suspect, when we're dressed our sexiest, we're dressing for other women, in a way. No, it is not a threesome fantasy-it's a competition. For you men, that is.

Once you've learned the secret language of a woman's clothing, you'll be a better judge of when she's signalling sexual interest. And that's helpful whether you're in a relationship, or looking for one. We've got some ladies to tell you about what women think when they wear what they wear, and here's what you know:

I'M WEARING Something red when everyone else is in black
I'm thinking I feel confident-and I want to be noticed.
"We have an intuitive sense of colour," says Dr Minnu Bhonsle, a psychologist at Heart To Heart Counselling Centre, Mumbai. Red, a hot colour, suggests that a person is outgoing, whereas blue, a cool colour, suggests that she's reserved. So people who wear red are trying to attract more attention to themselves than people who wear blues or greys.

Heck yeah, I sometimes feel like showing off, so I'll wear something to attract your attention. But since the colour of my clothing may also have a lot to do with fashion trends (purple is the new black-no, wait, pink is), you can't always tell a lot about a woman based on her chosen hue alone. Instead, take notice: How am I dressed compared with other women in the room? That's your clue.

Your move: This is really easy. Say, "You're the best-looking woman in the place." It's a can't-fail, evolution-based compliment that's guaranteed not to land you in the dog house. "Women are very aware of what other women are wearing," says Kristina Durante, a PhD candidate at the University of Texas at Austin. "We don't want to wear the same thing as someone else. Often the first thing we do when we walk into a room is determine where we stand in attractiveness compared with the other women around us."

I'M WEARING  High heels
I'm thinking Is he looking at my butt?
If you're noticing my body more than my shoes, they're working. Heels raise the buttocks so they become visually attractive to men, says Gad Saad, PhD, author of The Evolutionary Bases of Consumption.

But you already knew that, at least instinctively. This boost of the butt produces a curve of the lower back toward the abdomen which, in mammals, is the position of female sexual receptivity, Saad explains. It's no coincidence that strippers still wear stilettos after they've shed their clothing. Real-world evidence: I don't recall ever wearing a pair of flats on a first date.

Your move: Say, "Hot shoes" (after a few dates, it's acceptable to say "Your butt looks hot in those jeans"), and then take me somewhere fancy. "If she's wearing heels, she's not saying, 'I want to go to a mela, a guys' watering hole or to watch a cricket match at your place'," says Dr Bhonsle. "She's saying, 'I'm looking for sophistication, not down-home comfort.'" She's also saying, "I don't want to walk a kilometre to the next bar. Kindly hail us a taxi or be nice (and smart) enough to drive your car."

I'M WEARING A belted dress or skirt

I'm thinking I feel pretty, classically feminine and flirty.
Nothing makes me feel more ladylike than a dress, especially the belted variety, which slims the waistline, enhances curviness, and is currently in style. (Perhaps you noticed the big-belt trend if your girl dragged you to Fashion.) There is an evolutionary explanation for waist-cinching (corsets in the 19th century, wraparound dresses in the 1970s): Small waists appeal to men.

Dr Rohit Jaiman, consultant psychiatrist, Fortis, New Delhi, says curviness, reflected in a woman's waist-to-hip ratio (WHR), is somewhat dependent on her oestrogen levels. It can show "fecundity, or basically her overall fertility," he says. Some research shows that a WHR of about 0.7 (picture Mallika Sherawat or Lara Dutta... okay, you can stop now) is what is most universally appealing to the male gaze.

"Males enjoy looking at these types of bodies because mating with females with such body types is more likely to produce viable offspring than it would with those who don't," says Dr Jaiman.

David M Buss, PhD, author of The Evolution of Desire: Strategies of Human Mating, says that "belts and even colours and patterns can draw a man's attention to a woman's WHR, as well as give the appearance of a more pronounced WHR." A navel piercing may be her way of calling attention to her flat tummy, he says.

Your move: Be a gentleman. When I'm dressed up in a dress, I feel different, a more mature kind of sexy than when I'm wearing, say, hot jeans or short shorts. Accordingly, I want to be wooed by a more mature man. Old-school gestures are welcome: Wrap an arm around my waist, hold a door open. You'll charm my pants off. Oh, right, I'm not wearing pants. How convenient. (Yes, we have this thought, too.)

I'M WEARING A revealing V-neck top
I'm thinking Do you like what you see? Give me your sperm.
Okay, I'm not really thinking that, but my anxious ovaries sometimes are. Research shows that women reveal more skin and dress more sexily when they're near ovulation. The reason, according to University of Texas at Austin researchers: Women dress sexily to compete with other women for your attention.

"The single women are showing this shift more than women in relationships are," says Durante. "It shows that they're upping the ante, especially when they're going to a social event. It's possible they do this to have more in their arsenal to attract the best man they can."

Buss, a psychologist, says, "When women are ovulating, they are of higher 'mate value', so this is a perfect opportunity for them to attract high-quality mates."

But at this fertile moment, reproductive costs are high, says Durante. Translation: I don't want to mate indiscriminately and end up pregnant by some genetic loser who might not be able to provide for me.

"We want men who are going to provide the best genetic and material resources, but we're not all like Angelina Jolie and we can't all snag a Brad Pitt," Durante says. "So we dress up a little more, show off some cleavage, and pay a little more attention to our appearance. Then, perhaps, our mating pool is expanded."

Durante's study also showed that women who were less attractive dressed more sexily than attractive women, who don't need to try so hard.   

Your move Don't forget the condom. "If a woman you know is looking sexier than you've seen her look in a while, make sure you use due caution later in the night," says Durante. I may be programmed to be more motivated for sex when I'm ovulating, but it's also precisely the time you're most likely to father a child.

I'M WEARING A snug, soft top
I'm thinking Touch me.
I'm fully aware that when I wear my shortsleeved or sleeveless gray cashmere top or sweater, my boyfriend can't keep his hands off me. It's too easy, really. Women who wear soft, touchable fabrics could be advertising that they're feeling soft, gentle, very feminine, and not aggressive. That makes sense to me. A clingy sweater is one way I can show off quietly, without revealing a lot of skin. But there'll always be some ambiguity, Dr Jaiman points out.

Do I like the way a soft fabric feels against me? Or do I think you're going to like the way it feels against you? Perhaps a little of both. An over-the-fabric grope feels pretty nice for both parties, right?

Your move: I'm a sensual girl, so keep the hugs coming and be generous with postromp cuddles.

I'M WEARINGA blouse that reveals my bra strap

I'm thinking Come on, take a look at my shoulders . . . and of course my extremely sexy lingerie.
It doesn't take an evolutionary psychologist to make a snap judgment on this one. When I'm flashing just that hint of bra, it is most often like a starlet's red-carpet nip slip-intentional. (Exception to the rule: tan or nude-hued bras, which are decidedly unsexy and worn with the idea that their innate staidness will remain firmly hidden.) That hint of delicate pink lace at the tip of my V-neck shirt? I definitely want you to see it. Black bra under white, almost seethrough shirt: I want you to see that, too.

Even a white bra and panties can be sexy in a good-girl sort of way.

And when I (or better still, you) have taken off my top to reveal my sexy lingerie in its entirety, it is safe to assume that we have moved on from the look-but-don'ttouch to the touch-me-already portion of the programme.