addition
Pluraladditions
- 1Anything that is added to an existing thing, group, or whole.
The glass conservatory is a recent addition to the Victorian house.
Her latest addition to the collection was a rare first edition.
UsageUsually followed by to and the whole that grew: an addition to the house, the newest addition to the family.
Similarextension, acquisition, annex
- 2The act or process of adding one thing to another.
The recipe calls for the slow addition of the oil while you whisk.
The museum announced the addition of three new galleries to its east wing.
UsageMost often the addition of something: with the addition of two players. The set phrase in addition (to) means as well (as).
Similarinclusion, introduction
Oppositeremoval
- 3The arithmetic operation of combining two or more numbers to produce their sum.
Basic addition is taught alongside subtraction in the early grades.
He checked the restaurant bill with some quick mental addition.
UsageUsed with no article: children learn addition, do addition. An addition usually means a thing added.
Oppositesubtraction
Note
The operation written with the plus sign, and one of the most forgiving in mathematics. Order does not matter, since 3 + 5 and 5 + 3 give the same sum, so it is commutative. Grouping does not matter either, so it is associative. Adding zero changes nothing, which makes zero its identity element.
Less common meanings
- 4An organic chemical reaction in which two or more molecules combine to form a single larger molecule, called the adduct.
Bromine reacts with ethene by addition, yielding a single colorless product.
The addition of hydrogen across the double bond turns the alkene into an alkane.
Oppositeelimination
Note
Chemists name reactions by what happens to the molecules, and in this one nothing is lost: every atom of the reactants ends up in the adduct. The reaction typically takes place across a double or triple bond, which opens to take on the incoming atoms. Its converse is elimination, in which a molecule sheds atoms and usually a multiple bond forms.
Checked 5 Nov 2026 · 4 facts
- Addition describes the combination of reactants into one product without loss of atoms. openstax.org
- Addition typically occurs across a double or triple bond, reducing its multiplicity as new bonds form. ycmou.ac.in
- Elimination is the reverse of addition. chem.ucla.edu
- Elimination usually forms a multiple bond; α-elimination can instead produce a carbene, as in the elimination of HCl from chloroform. chem.ucla.edu
- 5A dot placed to the right of a note indicating that its duration is to be lengthened by one half.
- 6In heraldry, something added to a coat of arms as a mark of honor.
- 7A title annexed to a person's name, as in legal documents, to identify the person more precisely.
Practice
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Origin
The sense of "what is added" dates from the 14th century. It came through Middle English addicioun and Old French adition, from Latin additiō, ultimately from addō ("add, put").
Checked 5 Nov 2026 · 4 facts
- The sense “what is added” dates from the 14th century. en.wiktionary.org
- The word came through Middle English addicioun and Old French adition, from Latin additiō. en.wiktionary.org
- Latin additiō ultimately derives from addō. en.wiktionary.org
- Latin addō means “add” or “put.” en.wiktionary.org