THE Streetscapes column is not big on terminology, but some is necessary; instead of embarrassing yourself by saying “those grooves on the side of a column,” impress your dinner partner and use the real term, fluting.

FLUTING This is an apt term for shallow vertical channels, usually in a column; where else would you leave your flute? There’s a whole mess of fluting out in Morristown, N.J., where scores of column drums of Westchester marble, salvaged from a demolition site a century ago, lie strewn around like a collapsed project of wooden blocks.

Some of the best fluting in New York is not on a column at all, but the first-floor wall of the estimable 740 Park Avenue. The low, almost flat curves evoke the currents and eddies on the sea bottoms where this limestone was formed.

ORIEL OR BAY? We are speaking of those picturesque bumplike things on a facade, almost always with windows. Sometimes they continue all the way to the ground, sometimes they float in midair.

Here’s the trick: does it rest on its bottom? Then that’s B, for bay. Or, does it stick out from a higher floor on the facade with nothing under it? That’s O for oriel, with zero underneath. There are some great oriels on the 1880s houses on 95th off Park, especially 124 to 128.

One of the highest oriels in New York is on the north side of the Carlyle Hotel, jutting out from Apartment 34A: John F. Kennedy’s breakfast nook.

A particularly striking oriel is one added around 1900 to an old brownstone at 52 East 80th, with copper hammered into intricate shapes. I often imagine what it must be like inside, looking out the French windows from a wide leather seat, where I would take my coffee (light and sweet, please) and read The Times in the morning. And I mean the actual paper.

MANSARD Blame the mansard roof on the 17th-century French designer François Mansart, who gave drama and scale to his architecture by adding a floor with a sloping facade of slate shingles. In New York, it caught on in the mid-1860s, and as early as 1868 The Real Estate Record and Guide complained that mansard fad was pernicious: “the thing becomes so overdone that sheer nausea begets a change.”

Few listened — certainly not Carl Pfeiffer, the architect for the neat little group of mansarded pavilions for what is now Lenox Hill Hospital, at Park and 77th, of the same year.

Seven years later The Record and Guide said there had been no letup: “If the owner is penurious or the architect barren, there is one immediate way to make it known. Let them concoct a mansard.” The mansard has become the lifeline for developers and owners who want to add a floor or two — it offers some nice historical camouflage.

VITRUVIAN WAVE A range of identical wave-tops running along a band named, apparently in the 18th century, after the Roman architect Marcus Vitruvius Pollio. “Doing the wave” is a signature move in classical architecture, particularly English design of the late 18th century.

When William Delano brought his customary ingenuity to bear on his 1925 Brook club at 111 East 54th Street, he gave it a special touch: dolphins jumping from crest to crest. Even better is his polychrome band of waves around the Art Deco Marine Air Terminal at LaGuardia Airport, with flying fish.

RUSTICATION Do you like your pizza rustica? Then surely you like rustication, blocks of stone cut back at the edges to emphasize their mass. The term is mean to suggest “living in the country” — rustic, crude, undressed stonework. But my favorite is blocks that have been softly cut back with a gentle curve, so they look like giant stone pillows. The Federal Reserve Bank on Liberty Street has rustication like this.

Perhaps the most intense rustication in New York was visited upon the long-demolished house of William A. Clark, at Fifth Avenue and 77th Street. The Architectural Record observed that the building “had as its prototype rather a log-house than any extant construction of masonry.”

VERMICULATION Worms! Or, more precisely, a pattern carved into stone to imitate the twisting, turning tracks that worms make in soil, almost always found on rustication. The 1910 Carrère & Hastings building on Fifth Avenue for Knoedler & Company had perhaps the finest vermiculation in New York. Now the title falls to the 1904 town house at 647 Fifth Avenue; really, it’s entirely new, recreated in a 1996 restoration.

Ceiling Cornice Manufacturers Cheap Price

Just why someone thought that the worm- trail pattern was better than $, @, + and other motifs is difficult to answer.

A version of this article appears in print on April 29, 2012, on Page RE5 of the New York edition with the headline: Useful Vocabulary For Building Watchers. Order Reprints| Today's Paper|Subscribe

Pu Foam Corbel, PU Cornice Mouldings, PU Comers, Corner Flower - Ouzhi,