Rosewood refers to any of a number of richly hued timbers, often brownish with darker veining, but found in many different hues. All rosewoods are strong and heavy, taking an excellent polish, being suitable for guitars, turnery (billiard cues, the black pieces in chess sets, etc), handles, furniture, luxury flooring, etc.
In general, supplies are poor through overexploitation. Some species become canopy trees (up to 30 m high), and large pieces can occasionally be found in the trade.
All genuine rosewoods belong to the genus Dalbergia. The pre-eminent rosewood appreciated in the western world is the wood of Dalbergia nigra which is now a CITES-listed endangered species. It is best known as Brazilian Rosewood, but also as "Rio Rosewood" or "Bahia Rosewood." This wood has a strong sweet smell, which persists over the years, explaining the name "rosewood".
Another classic rosewood is that yielded by Dalbergia latifolia known as (East) Indian Rosewood or Sonokeling. Note that not all species in the large genus Dalbergia yield rosewoods; only about a dozen species do. They can be found in tropical America, Southeast Asia, and Madagascar. The woods of some other species in the genus Dalbergia are notable—even famous—woods in their own right: African Blackwood, Cocobolo, Kingwood, and Tulipwood. The Indian souvenir trade tries to sell objects made of Dalbergia sissoo (sometimes stained purple) as if they were rosewood. The wood of some other species is usable for toolhandles at best.
The timber trade will sell many timbers under the name "rosewood" (usually with an adjective) due to some (outward) similarities. A fair number of these timbers come from other legume genera; one such species that is often mentioned is Machaerium scleroxylon. Another that may be found in advertisements from Asia is Pterocarpus indicus (and related species).
An exception is the Australian Rose Mahogany (Dysoxylum fraserianum), a highly regarded rainforest tree in eastern Australia which is sometimes also called "Rosewood" although its wood bears no resemblance whatsoever to the true rosewoods.