Sao

1. A nereid (sea nymph) in Greek mythology.
2. astronomyA moon of Neptune, named after the nymph.

1. rareAny marine annelid of the genus Hyalinoecia, especially Hyalinoecia tubicola of Europe, which inhabits a transparent movable tube resembling a quill in color and texture.

   Amongst the other genera belonging to this group of Euniceans, there are one or two which inhabit tubes. Such is the Sao (Northia tubicola of Johnston, the Nereis tubicola of Müller), and the Onuphis conchilega of Sars.

   1869, William Baird, “The Annelidan Worms, or Annelides (Annelida)”, in The Student and Intellectual Observer, volume 3, London: Groombridge & Sons, →OCLC, page 169

   2 more examples

   The use of the tube is to protect the body from the pressure of the soft mud in which it stands immersed. When the tube is overset or cast out by the waves or accident, the worm leaves it, and becomes, in its turn, exposed to enemies. To protect itself from these while a new tube is being secreted, nature has amply furnished the Sao with a series of bristling lances on each side. These arms are of exquisite make, very fine and very sharp; and those of the upper bundle have their points bent and inclined towards those of the lower bundle, which are likewise bent to meet them.

   1865, George Johnston, A Catalogue of the British Non-Parasitical Worms in the Collection of the British Museum, London: Taylor & Francis, →OCLC, page 138

   The family Eunicidæ is distinguished by a long and numerously segmented body, and a distinct and projecting head. […] The Sao, [Northia tubicola] one of this family, lives in a tube which it constructs for itself, and which presents the exact appearance of a quill pen.

   1896, Peter Martin Duncan, editor, Cassell's Natural History, volume 6, London: Cassell & Co., →OCLC, pages 230–231

plural SAOs

1. abbreviationinitialismuncountableInitialism of session-at-once, a recording mode for optical discs.
2. UKabbreviationcountableinitialismuncountablegovernmentInitialism of Specified Associated Organisation.
3. abbreviationcountableinitialismuncountableeducationInitialism of school attendance order.

1. Serb Autonomous Oblasts
2. Smithsonian Astrophysical Observatory (or the star catalog)
3. Special Astrophysical Observatory of the Russian Academy of Science
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