How do I love thee? Let me count the ways.

You are reliable, there with me from weddings to funerals. You are sexy, yet sophisticated. I look thinner when we are together. If I do gain a few pounds, you are forgiving. You are beloved by women all over the world, yet you are always there for me. I cannot live without you.

This is every woman’s Ode to the Little Black Dress — and the reason for its longevity.

“One is never over-dressed or under-dressed with a Little Black Dress,” Karl Lagerfeld, the German designer with a label of his own and currently the director of the House of Chanel, once said. It was Coco Chanel herself who turned the LBD into an iconic fashion statement in 1926.

Today, the LBD crosses generations, as popular with millennials as boomers. Millennials, however, seem to get more mileage out of theirs.

“I’ve worn it (the little black dress) to weddings and to sleep in,” says Emilie Morgen Wallin, of the jersey maxi dress offered in her debut Nylon Riot collection of modern, eco-friendly clothing.

When the New Orleans native, who resides in Los Angeles, brought her new label home recently for a trunk showing, two black dresses stood out: a sweatshirt-style dress with asymmetrical panels, and the aforementioned maxi that can be worn half a dozen different ways.

Wallin designed the jersey maxi to be all things to all women. One side of the dress has a scoop neckline. Turn it around, and it’s a V-neck. Tie the waist with the black 1930s grosgrain ribbon for a more feminine silhouette, or leave it loose for an oversized look.

Wear it as a racerback halter by tying up the back. There’s even a matching bandeau that can be worn underneath for extra coverage when desired.

As previously stated by the 25-year-old designer, “It makes a pretty amazing nightgown, too.”

“I think the little black dress should be simple and effortless,” says Wallin, who sees the LBD as a way to cut down on closet clutter. “I don’t want to open my closet and see a ton of pieces that create the what-should-I-wear confusion. I think you should view your closet with a Parisian state of mind.”

Versatile ease

Local boutique owner Hattie Collins Moll agrees that the Chanel concept still applies today.

“The LBD should be transitional and versatile,” says Moll, who recently relocated her four-year-old boutique, Hattie Sparks, from Uptown to the South Market District.

The black dresses in her current inventory depart from the usual solid with patterns and textures — a short dress in black lace over a nude-colored lining, or a black mini accented with contrasting embroidery.

Moll’s personal closet contains about half a dozen LBDs.

“I prefer a sleeveless version with a boat neck in a classic A-line,” says Moll, 30, who goes for a mid-weight fabric to keep it seasonless.

She changes her leg coverings from sheer to textured to opaque to patterned tights, keeps a cashmere wrap on hand for cooler months, and bright options in jewelry and shoes for more festive occasions.

‘Fun and flirty’

“A little black dress should be fun and flirty,” says Agnes Backman, 37, co-owner of Folklore hair salon on Freret Street.

She took note five years ago that her closet was minus an LBD. Backman went out and bought two.

So versatile is the dark solid basic, Backman bought another one for Mardi Gras as the foundation to a costume.

“I wore it with layered fun tights, purple socks peeking out under my boots, and added a leopard-print shawl and a funky hat,” say Backman. The dress, she says, is one that will return to its basic state and be reinterpreted for future occasions, elegant or eclectic.

Show-stopping shifts

The Little Black Dress is a prized basic, but it is also a show-stopper.

Over decades, women in black have made legendary entrances: Givenchy-clad Audrey Hepburn in “Breakfast at Tiffany’s” in 1961, Princess Diana sporting bare shoulders and cleavage at a 1994 Vanity Fair party the day after the Prince had confessed his adultery (the sexy black dress went down in fashion history as the “revenge dress”), Carolyn Jones as Morticia in ‘60s TV series “The Addams Family,” Marilyn Monroe in something sheer in “Some Like It Hot” (1959), Demi Moore in a seductive Thierry Mugler cut-out dress in 1993 in “Indecent Proposal,” Tina Turner on her final tour in 2009 in a sparkling black minidress and signature power heels, and Lady Gaga in a retro-glamour corseted Versace gown at the recent Golden Globes.

When Bruce Jenner invited Diane Sawyer into his closet last April for the 20/20 taping, he showed Sawyer the slinky little black dress he planned to wear for his debut as Caitlyn.

In its purest form, the LBD is a solid with simple lines and a hemline that hovers at the knee.

With 20-somethings, however, it’s hard to tell that a timeless fashion piece is the core of an outfit.

“Who knew? The way it is accessorized you forget it’s a plain black dress,” says Jennifer Casey of GaeTana, a contemporary boutique located in the University Section, where coeds are part of the clientele.