Shortcuts

The word ''mini'' never passes their lips. Yet many a designer is indulging in length-cropping sprees the likes of which have not been seen since Mary Quant and Andre Courreges made history in the 1960s.

What to call the new swinging shorts that seem to be part skating skirt, part culotte? How to define the cross-breedings of dirndl and ballet skirt? They are not, in fact, latter-day versions of the little-girl clothes worn 15 years ago when fashion turned women into children with small bodies, long legs, and large heads (via bombe hairdos and Breton hats).

Geoffrey Beene's skinny shift with its hip wrap has echoes of the 1920s flapper. But the short and narrow skirt now favored by France's Yves Saint Laurent and by America's James Galanos has no real precedent. Both designers see it as companionable with a broad-shouldered hip-length jacket or as an underskirt for a tunic top. When the slim, abbreviated skirt is slit, wrapped, or tulip-shaped, it often comes with a matching pair of little shorts. At Galanos, the shorts are apt to be of the best printed silk from Abraham, the prestigious Swiss firm. These are not elegant play clothes. Luxurious street wear, afternoon and early evening dress - those are the designers' intentions.

Neither are the short little chemise dress with a ruffle at the hem nor the bubble-shaped dress sportswear styles. Worn with dark stockings, these styles are citified looks.

A considerable time would have to pass before that much knee and leg, not to mention thigh, is exposed by the great majority of women. Meanwhile, short shorts and flared skirts, bloomers, pleated culottes that end above the knee, and all the other varieties of brief new separates pieces are top fashion candidates for a spring-summer wardrobe.

For the rest, shorter skirts that show at least a bit of knee make sense in warm weather. Just-below-the-knee length is, in any case, likely to look dowdy this year. Either shorter, or a lot longer - depending on the person's height and weight - has more dash.

A lot longer (mid-calf or above-ankle) has also been universally endorsed as a second top choice in lengths. It has become the thing among designers to hedge their bets by proclaiming that ''hemlines don't matter.'' Yet while showing short, medium, and long, many concentrated on one particular length: Ralph Lauren, above-the-ankle; Calvin Klein, more often mid-calf than short or medium. Perry Ellis came out categorically for a below-calf, straight, narrow skirt for spring.

But for his summer collection, Ellis reversed himself by presenting scores of ultrashort clothes as if he were saying, ''This just shows you: length doesn't mean a thing.''