| opal |
a mineral that is white, black, blue, or yellow. Opals are used as gems. |
| opaque |
not letting light pass through. [2 definitions] |
| OPEC |
an association made up of several Arab nations that sell the oil they produce to other countries. "OPEC" is an abbreviation of "Organization of Petroleum Exporting Countries." |
| open |
allowing something or someone to pass through or to get to the inside; not shut or closed. [16 definitions] |
| opener |
someone or something that opens. [3 definitions] |
| opening |
the act, process, or result of making open or causing to become open. [5 definitions] |
| openly |
in a way that involves no hiding or lying. |
| open-minded |
not having made opinions or decisions ahead of time; willing to consider new ideas. |
| opera1 |
a play in which all or most of the words are sung and the music is played by an orchestra. |
| operate |
to work or run. [3 definitions] |
| operation |
the act or process of working or running. [4 definitions] |
| operator |
someone who controls the working of a machine or the activities of a business. [2 definitions] |
| operetta |
a short, funny opera, with words that are spoken as well as sung. |
| ophthalmologist |
a doctor who works in the branch of medicine that studies and treats diseases of the eye. |
| ophthalmology |
the branch of medicine that studies and treats diseases of the eye. |
| opinion |
what one thinks about something or somebody; viewpoint. An opinion is not necessarily based on facts. Feelings and experiences usually help a person form an opinion. [3 definitions] |
| opossum |
a small mammal with gray fur, a pointed nose, and a long tail, which it uses to hang from tree branches. The common opossum is the only marsupial that lives in North America. Several other kinds of opossums live in Central and South America. The female opossum carries her young in a pouch in her belly. [2 definitions] |
| opponent |
one who fights, plays, or takes a position against another. |
| opportunity |
a chance for a better situation. [2 definitions] |
| oppose |
to think, act, or be against; resist. [2 definitions] |
| opposed |
not in favor of; against. |