Surgical instrument or medical implement used to induce dilation, that is, to expand an opening or passage such as the cervix (see cervical dilator), urethra, esophagus, or vaginal introitus.
A speculum is a medical tool for investigating body orifices, with a form dependent on the orifice for which it is designed. In old texts, the speculum may also be referred to as a diopter or dioptra. Like an endoscope, a speculum allows a view inside the body; endoscopes, however, tend to have optics while a speculum is intended for direct vision.
Specula have been made of glass or metal. They were made of stainless steel and sterilized after use. However, in the 21st century, many especially those used in emergency departments and doctor's offices are now made of plastic, and are disposable, single-use items. Those used in surgical suites are still commonly made of stainless steel.