A cocktail dress is at once a formal piece of clothing and a casual outfit. It's almost easier to define what a cocktail is not than it is to say specifically what it should be. Sit-down events like charity dinners and cocktail parties may call for dressier materials and styles. An evening out with friends at a ritzy bar or a blind date may suggest something more spunky and modern.

For some cocktail affairs, you can show up in your business suit and blend right in. For weekend get-togethers or planned dates, however, you might be more mindful of setting. For summer cocktail parties, you can choose bright colors, such as light green, floral patterns and pastels. For evening and winter cocktail parties, you may go with more muted tones, such as brown, crimson or navy blue.

Some major types of cocktail dresses include short and spicy, vintage, spaghetti strap, sundresses, wool blended dresses, satin pants with a coordinating top or sweater, and the ever appropriate little black dress. Generally, anything that is slightly shorter than a full-length gown and longer than a mini-skirt may be considered a cocktail dress, depending on the circumstances and wearer.

Lane Bryant, Roberto Cavalli, DSquared, and Chloe all craft unique, trendy, and interestingly tailored cocktail dresses. With a fun cocktail dress, you can diversify your wardrobe by going against the grain of your normal fashion idiosyncrasies. Above all, though, do not forget to accessorize! Companies like DKNY, Isabella Fiore, and Marni make exquisite cocktail dress accessories.