Is a chaise longue the same as a chaise lounge?

Yes. The two spellings cover the same object, and dealers split between them: 361 titles say "longue" and 122 say "lounge". There is no difference in what is offered under either. Searching one spelling alone will miss a good share of the category.

Why do some listings call it a sofa or day bed?

The naming shades across neighbouring forms. "Sofa" appears in 83 titles, "settee" in 39, "day bed" in 23 and "couch" in 21, often on the same piece. Day bed tends to get used where the piece is long and low or has a raised end at both sides. Double-ended examples are the ones most likely to be described as a small sofa.

What period are most of them?

The evidence is heavily 19th-century. "Victorian" appears in 246 titles, and in the dealers' dating field Victorian at 149 and "19th Century" at 125 together outnumber every decade bucket. Regency is the main pre-Victorian block with 62 entries, and Edwardian and 1900s pieces form a small tail. Where a decade is named, the 1860s dominates with 57 listings, more than the 1850s and 1870s combined.

Which timbers turn up most often?

Mahogany, walnut and rosewood cover most of the category, with 141, 93 and 66 titles. A plain Victorian example in mahogany or walnut is the commonest thing on offer. Everything else is a curiosity. Oak, beech, satinwood, pitch pine and solid Rio rosewood each surface only once or twice.

How many come up for sale each year?

Around 57 chaises come to market on Sellingantiques in a year. They are spread across 136 different dealers, so no single dealer defines what the category looks like.

Do unusual shapes ever appear?

They do, but singly rather than in runs. The archive holds a bath tub chaise, a kidney-shaped one, an iron-back example, a bentwood one and a hybrid settle-and-chaise. Also recorded: a miniature ebonised model, an adjustable reclining day bed, and three separate examples with concealed storage. Continental and colonial one-offs are the rarest origins, against 27 French and 29 explicitly English titles.