dadj. denoting a quantity consisting of 500 items or units ; Dn. the 4th letter of the Roman alphabet ; Dn. the cardinal number that is the product of one hundred and five ; Dn. a fat-soluble vitamin that prevents rickets ; D and Cn. a surgical procedure usually performed under local anesthesia in which the cervix is dilated and the endometrial lining of the uterus is scraped with a curet ; performed to obtain tissue samples or to stop prolonged bleeding or to remove small tumors or to remove fragments of placenta after childbirth or as a method of abortion ; D regionn. the lowest region of the ionosphere (35 to 50 miles up) that reflects low-frequency radio waves ; d'Holbachn. French philosopher (born in Germany) famous as being one of the first self-described atheists in Europe ; D'Oyly Carten. English impresario who brought Gilbert and Sullivan together and produced many of their operettas in London (1844-1901) ; D-dayn. date of the Allied landing in France, World War II ; D-layern. the lowest region of the ionosphere (35 to 50 miles up) that reflects low-frequency radio waves ; D. H. Lawrencen. English novelist and poet and essayist whose work condemned industrial society and explored sexual relationships (1885-1930) ; D. W. Griffithn. United States film maker who was the first to use flashbacks and fade-outs (1875-1948) ; D.A.n. a doctor's degree with a special disciplinary focus ; D.C.n. the district occupied entirely by the city of Washington ; chosen by George Washington as the site of the capital of the United States and created out of land ceded by Maryland and Virginia ; d.j.n. a person who announces and plays popular recorded music ;