ATOM

n. smallest part of an element (Physics, Chemistry); something that is extremely small, minute or microscopic object

In chemistry and physics, an atom (Greek ἄτομος or átomos meaning "indivisible") is the smallest particle still characterizing a chemical element.An atom consists of a dense nucleus of positively-charged protons and electrically-neutral neutrons, surrounded by a much larger electron cloud consisting of negatively-charged electrons. An atom is electrically neutral if it has the same number of protons as electrons. The number of protons in an atom defines the chemical element to which it belongs, while the number of neutrons determines the isotope of the element.
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The name Atom applies to a pair of related standards. The Atom Syndication Format is an XML language used for web feeds, while the Atom Publishing Protocol (APP is the acronym, but it is referred to as 'AtomPub' for short) is a simple HTTP-based protocol for creating and updating Web resources. Web feeds allow software programs to check for updates published on a web site. To provide a web feed, a site owner may use specialized software (such as a content management system) that publishes a list (or "feed") of recent articles or content in a standardized, machine-readable format. The feed can then be downloaded by web sites that syndicate content from the feed, or by feed reader programs that allow Internet users to subscribe to feeds and view their content.
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Noun
1. (physics and chemistry) the smallest component of an element having the chemical properties of the element
(hypernym) substance, matter
(hyponym) isotope
(part-holonym) chemical element, element
(part-meronym) elementary particle, fundamental particle, subatomic particle
(derivation) atomize, atomise
(classification) physics, physical science, natural philosophy
2. (nontechnical usage) a tiny piece of anything
(synonym) molecule, particle, corpuscle, mote, speck
(hypernym) material, stuff
(hyponym) grain
(derivation) atomize, atomise

n. something that is extremely small, minute or microscopic object; (Physics, Chemistry) atom, smallest part of an element

n. atom, atomy; monad

adj. atomic, nuclear, atomical