os

¹ American  

[os] / ɒs /

noun

plural

ossa

1. Anatomy, Zoology. a bone.

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os ² American  

[os] / ɒs /

noun

plural

ora

1. Anatomy, Zoology. a mouth or orifice of the body.

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os ³ American  

[ohs] / oʊs /

noun

plural

osar

1. Geology. an esker, especially when of great length.

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Os ⁴ American  

1. Symbol, Chemistry. osmium.

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OS ⁵ American  

abbreviation

1. Old Saxon. Also O.S.

2. Computers. operating system.

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o/s ⁶ American  

1. (of the calendar) Old Style.

2. out of stock.

3. (in banking) outstanding.

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O/S ⁷ American  

1. (of the calendar) Old Style.

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O.S. ⁸ American  

Or o.s.

abbreviation

1. (in prescriptions) the left eye.

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O.S. ⁹ American  

abbreviation

1. Old Saxon. Also OS

2. (of the calendar) Old Style.

3. ordinary seaman. Also o.s.

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OS ¹ British  

abbreviation

1. Old School

2. Old Style (method of reckoning dates)

3. Ordinary Seaman

4. (in Britain) Ordnance Survey

5. outsize

6. Old Saxon (language)

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o.s. ² British  

abbreviation

1. out of stock

2. banking outstanding

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Os ³ British  

symbol

1. osmium

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os ⁴ British  

/ ɒs /

noun

1. anatomy the technical name for bone

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os ⁵ British  

/ ɒs /

noun

1. anatomy zoology a mouth or mouthlike part or opening

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os ⁶ British  

/ əʊs /

noun

1. another name for esker

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Etymology

Origin of os¹

First recorded in 1540–50; from Latin os (inflectional stem oss- ) “bone”

Origin of os²

First recorded in 1730–40; from Latin ōs (inflectional stem ōr- ) “mouth”

Origin of os³

First recorded in 1840–50 as osar (plural); from Swedish ås (plural åsar ) “ridge (of a hill),” from Old Norse áss “thick pole or main beam; rocky ridge”

Origin of O.S.⁸

From Latin oculus sinister

Example Sentences

A new Longevity Preparedness Index from John Hancock and MIT AgeLab os based on a survey of over 1,300 adults and focused on eight areas such as finance, home, health and community.

From MarketWatch • Dec. 12, 2025

She first broke through with 2016’s “Remonta,” an album she recorded with her former band Liniker e os Caramelows.

From Los Angeles Times • Oct. 8, 2025

De todos os peixes da região, sete espécies de pacu são as mais importantes para sua comunidade, que depende principalmente da pesca para subsistência.

From Science Magazine • Jan. 5, 2023

Conhecidos como piranhas vegetarianas, os pacus podem atingir até um metro de comprimento.

From Science Magazine • Jan. 5, 2023

Newton disliked infinitesimals, the little os in his fluxion equations that sometimes acted like zeros and sometimes like nonzero numbers.

From "Zero: The Biography of a Dangerous Idea" by Charles Seife