\ˈbās \
plural bases\ ˈbā-​səz \

Definition of base 

(Entry 1 of 4)

1a architecture

(1) : the lower part of a wall, pier, or column considered as a separate architectural feature

(2) : the lower part of a complete architectural design (as of a monument)

b : the bottom of something considered as its support : foundation the base of the mountain the lamp's heavy base

c mathematics

(1) : a side or face (see face entry 1 sense 5a(5)) of a geometrical figure from which an altitude (see altitude sense 1c(1)) can be constructed especially : a side or face on which the figure stands the base of a triangle

(2) : the length of a base determining the triangle's base

d biology : that part of a bodily organ by which it is attached to another more central structure of the organism the base of the thumb

2a : a main ingredient paint having a latex base

b : a supporting or carrying ingredient (as of a medicine)

c : a first or bottom layer of something on which other elements are added Overnight, Utah's famous snow has freshly blanketed both runs, adding to a solid base of three feet …— Abby Carroll

3a : the fundamental part of something : groundwork, basis the book's theoretical base her broad base of knowledge

b : something (as a group of people) that reliably provides support (such as for a business or political candidate) usually singular efforts to expand their customer basethe band's fan baseBut I do believe that that's a very sore point with many Democrats and could be used to energize their base.— John McCain

c Marxism : the economic factors on which all legal, social, and political relations are formed

4 heraldry : the lower part of a heraldic field (see field entry 1 sense 3c)

5a : the starting point or line for an action or undertaking plans to make this city his base of operation— J. A. Loftus

b : a baseline in surveying

c : a center or area of operations The company has its base in London. : such as

(1) : the place from which a military force draws supplies

(2) : a place where military operations begin

(3) : a permanent military installation a naval base The troops were ordered back to base.

d mathematics

(1) : a number (such as 5 in 56.44 or 57) that is raised to a power (see power entry 1 sense 5a) especially : the number that when raised to a power equal to the logarithm of a number yields the number itself The logarithm of 100 to the base 10 is 2 since 102 = 100.

(2) : a number equal to the number of units in a given digit's place (see place entry 1 sense 8) that for a given system of writing numbers is required to give the numeral 1 in the next higher place The decimal system uses a base of 10. also : such a system of writing numbers using an indicated base Convert from base 10 to base 2.

(3) : a number that is multiplied by a rate or of which a percentage or fraction is calculated To find the interest on $90 at 10 percent multiply the base 90 by .10.

e linguistics : root sense 6 "Leave" is the base of the verb "left."

6a in various games : the starting place or goal

b : any one of the four stations at the corners of a baseball or softball infield allowing the batter to reach base

c : a point to be considered His opening remarks touched every base.

7 chemistry

a : any of various typically water-soluble and bitter tasting compounds that in solution have a pH greater than 7, are capable of reacting with an acid to form a salt, and are molecules or ions able to take up a proton from an acid or able to give up an unshared pair of electrons to an acid

b : any of the five purine or pyrimidine bases of DNA and RNA that include cytosine, guanine, adenine, thymine, and uracil

8 finance : a price level at which a security (see security sense 3) previously declining in price resists further decline

9 linguistics : the part of a transformational grammar that consists of rules and a lexicon and generates the deep structures of a language

10 : an electrode that modulates the current flowing through a bipolar junction transistor according to the voltage applied to the electrode This gate, which is called a grid in a tube and a base in a transistor, enables a small "controlling" voltage to turn on and off a much larger voltage between the cathode and the anode.— Thom Hartmann — compare gate entry 1 sense 5b

cover all the bases or less commonly cover every base or have (all) one's bases covered

: to do or include everything that needs to be done or included : to fulfill all requirements or necessities The well rounded menu covers all the bases—pork or duck breast and always a grilled chicken with complementary sauces and relishes …— Caroline Bates In other words, we need to cover every base. Too often, something is remembered at the last minute and we find ourselves waiting for the stores to open on sale day so we can purchase a much-needed item.— Sue Story In your e-mail, let the company know that, for their convenience, you're e-mailing the resume and letter, but that the original documents will arrive by postal service. This way you've got all your bases covered.— Peter Post

off base

1 : wrong, mistaken Estimates were way off base.

2 : unawares caught off base by the charges

touch all the bases or less commonly touch every base

1 : to mention every subject that needs to be considered a speech that touches all the bases

2 : to do or include everything that needs to be done or included : to fulfill all requirements or necessities need to touch all the bases when applying for a mortgage The owner of the Utah Stars is in Salt Lake City, working 24 hours a day in an effort to touch every base to keep his club in Utah's capital city.— Dan Pattison


based; basing

Definition of base (Entry 2 of 4)

transitive verb

1 : to make, form, or serve as a base for … great roots based the tree columns …— George Macdonald the company is based in London clients who are based out of their homes

2 : to find a foundation or basis for : to find a base (see base entry 1 sense 3a) for usually used with on or upon base an opinion on faulty informationa story based upon real-life events


adjective (1)

Definition of base (Entry 3 of 4)

1 archaic : of little height … the cedar stoops not to the base shrub's foot …— Shakespeare

2 obsolete : low in place or position … fall to the base earth from the firmament!— Shakespeare

3 obsolete : bass

4 archaic : baseborn base in kind and born to be a slave.— William Cowper

5 feudalism

a : resembling a villein : servile a base tenant

b : held by villenage base tenure

6a : being of comparatively low value and having relatively inferior properties (such as lack of resistance to corrosion) a base metal such as iron — compare noble entry 1

b : containing a larger than usual proportion of base metals base silver denarii

7a : lacking or indicating the lack of higher qualities of mind or spirit : ignoble seemed a base betrayal of idealism— L. M. Sears appealing to a person's baser instincts

b : lacking higher values : degrading a drab base way of life


adjective (2)

Definition of base (Entry 4 of 4)

1 : constituting or serving as a base This situation is frequently encountered by seaplane pilots in northern Canada who must fly over lakes and tundra to a base camp located on a river.— Alan Lopez

2 : of the simplest or most basic design or form : having the form of something before upgrades or customization This GTO's 350-hp, 5.7-liter V8 is the same that's used in the base Corvette, and it produces the power and throaty exhaust sound of a classic muscle car.Consumer Reports

Illustration of base

Illustration of base


base of a column: 1 upper torus, 2 scotia, 3 lower torus, 4 plinth, 5 shaft, 6 fillets

In the meaning defined above

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Other Words from base


based \ ˈbāst \ adjective
baseless \ ˈbā-​sləs \ adjective

Adjective (1)

basely adverb
baseness noun

Choose the Right Synonym for base

Adjective (1)

base, low, vile mean deserving of contempt because of the absence of higher values. base stresses the ignoble and may suggest cruelty, treachery, greed, or grossness. base motives low may connote crafty cunning, vulgarity, or immorality and regularly implies an outraging of one's sense of decency or propriety. refused to listen to such low talk vile, the strongest of these words, tends to suggest disgusting depravity or filth. a vile remark

Examples of base in a Sentence


the firm belief that complete trust between husband and wife is the base of any successful marriage the army's base of attack was kept top secret until the battle began


They are going to base their new company in Seattle. The company has based itself in London. Our tour group based itself in a hotel in the heart of the city.

Adjective (1)

Iron is a base metal. a base and sneaky act that is a clear violation of international law
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Recent Examples on the Web: Noun

Those who are up for re-election in the House don’t want to get out in front of the base. Andrew Duehren, WSJ, "Some GOP Lawmakers Seek to Rein In Trump on Trade," 13 July 2018 In the midterms, the motivation of the base can make the difference in close races. Jeet Heer, The New Republic, "Democrats enjoy a huge party registration advantage in midterms.," 10 July 2018 The halibut is served on a base of cous-cous compesto. CBS News, "A Taste of Summer: Cultivating the perfect park experience," 8 July 2018 However, the bone at the base of our big toe—called the medial cuneiform—has a connection for the big toe that is more curved and slightly more angled than what is found in humans today. Jason Daley, Smithsonian, "Ancient Toddler Was at Home on the Ground and in the Trees," 5 July 2018 On Wednesday, a person climbed the Statue of Liberty’s base shortly after the arrests of several people who hung a banner from the pedestal calling for abolishing Immigration and Customs Enforcement, the Associated Press reported., "Contractors housing migrant children are close to Trump’s inner circle," 4 July 2018 The need to maintain military secrecy prevented civilian firefighters from entering the scene, and fire leaped from building to building, incinerating most of the base. Lucy Cooke, ajc, "US military is interested in bats as possible defenders against bioweapons," 3 July 2018 Everything from how to throw to taking a lead on the bases. David Hinojosa, San Antonio Express-News, "New Braunfels native makes big strides on USA Baseball women’s national team," 3 July 2018 Trump has used tough rhetoric on immigration to motivate his political base at home, at times using racial or ethnic undertones. Washington Post, "Trump stands by ‘culture’ criticism of European immigration," 13 July 2018

Recent Examples on the Web: Verb

The 2000 Van Hool bus was operated by QH Express, based in Rosemead, according to federal traffic safety records. Maya Lau And Irfan Khan,, "Tour bus driving from Pala Casino crashes in L.A., injuring 25," 14 July 2018 The carbon-free energy, however, regularly causes migraines for operators at the Bonneville Power Administration, based in Portland, Ore., who manage the regional electricity grid. Peter Fairley, Scientific American, "Weather-Smart Electric Grids Are Needed for Wind and Solar Power to Surge," 13 July 2018 Meanwhile, Sacred Games is also facing a police complaint filed by another Congress party member, Rajeev Sinha, based in the western city of Kolkata. Nyay Bhushan, The Hollywood Reporter, "Netflix Series Faces Legal Case Over Portrayal of Ex-India Prime Minister," 13 July 2018 Gina Adams, a Native-American artist based in Kansas, takes antique quilts and overlays them with texts from actual historical treaties – mostly broken. George Fishman, miamiherald, "Monarchs ‘Brown and Native’ butterfly exhibit a response to contemporary events," 13 July 2018 Though the business of pizza-making has not yet been robotised completely, Zume Pizza, also based in California, is getting close. The Economist, "The rise of the robochef," 12 July 2018 On June 28, the U.S. military’s Indo-Pacific Command deployed 36 personnel based in nearby Okinawa, including airmen from 353rd Special Operations Group and the 31st Rescue Squadron. Kyle Mizokami, Popular Mechanics, "How the U.S. Military Helped Support the Thai Cave Rescue," 11 July 2018 Andy Patrizio is a freelance technology journalist based in Orange County, California, not entirely by choice. Andy Patrizio, Ars Technica, "The AI revolution has spawned a new chips arms race," 9 July 2018 Borgia is a long-time developer based in Yaphank, N.Y., and he’s been involved in the development of at least one sports complex on Long Island. Gregory B. Hladky, Courant Community, "A Long Island Developer Wants To Build A $200 Million Sports Complex In Windsor Locks," 9 July 2018

Recent Examples on the Web: Adjective

The base level measures 50 by 120 meters at its maximum. Charles Stanish, Smithsonian, "How Feasting Rituals Help Shape Human Civilization," 5 July 2018 Royals manager Ned Yost thought Billy Hamilton was out of the base path. Pete Grathoff, kansascity, "Was Cincinnati's Billy Hamilton out of the base path on this controversial play?," 13 June 2018 Under the new plan, the base monthly rent for tenants eligible for reduced rates will be $130 for an efficiency and $150 for a one-bedroom unit. Bill Leukhardt, Courant Community, "Waiting List Open For Southington Housing Authority Apartments," 13 July 2018 For its new Ginger Zest, Belvedere separately distills fresh ginger, pink grapefruit, lemon, and honey vodkas then blends them with more base spirit, much as a blended whiskey would be made. Elva Ramirez, charlotteobserver, "Flavored vodka is moving on from its whipped cream, PB&J past," 6 July 2018 The IdeaPad 330 is the cheapest model, starting at $249.99 for the base 15-inch model. Chaim Gartenberg, The Verge, "Lenovo has some new IdeaPads for every budget," 11 May 2018 For 2018, Suburban prices begin at $50,200 (plus freight) for the base rear-wheel-drive LS model. G. Chambers Williams Iii, Houston Chronicle, "2018 Suburban: SUVs looks great with Z71 Midnight Edition package," 30 Apr. 2018 For 2018, Suburban prices begin at $50,200 (plus freight) for the base rear-wheel-drive LS model. G. Chambers Williams Iii, star-telegram, "Chevrolet’s 2018 Suburban looks great with the Z71 Midnight Edition package | Fort Worth Star-Telegram," 24 Mar. 2018 That -- a bargain for a veteran rotation defensive tackle -- will now be Spence's base salary with the Dolphins. Armando Salguero, miamiherald, "Defensive tackle was Miami Dolphins biggest post-draft need. Not anymore | Miami Herald," 3 May 2018

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'base.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

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First Known Use of base


14th century, in the meaning defined at sense 1a(1)


1587, in the meaning defined at sense 1

Adjective (1)

14th century, in the meaning defined at sense 1

Adjective (2)

1734, in the meaning defined at sense 1

History and Etymology for base


Middle English, from Anglo-French, from Latin basis, from Greek, step, base, from bainein to go — more at come


verbal derivative of base entry 1

Adjective (1)

Middle English bas, from Anglo-French, from Late Latin bassus fat, short, low

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Statistics for base

Last Updated

7 Nov 2018

Look-up Popularity

Time Traveler for base

The first known use of base was in the 14th century

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More Definitions for base



English Language Learners Definition of base

 (Entry 1 of 3)

: the bottom or lowest part of something : the part on which something rests or is supported

: something (such as a group of people or things) that provides support for a place, business, etc.

: a main ingredient to which other things are added to make something



English Language Learners Definition of base (Entry 2 of 3)

: to have a particular place as the main place where a person works or lives or where a business operates



English Language Learners Definition of base (Entry 3 of 3)

: not honest or good

of a metal : having low quality and value


\ˈbās \

Kids Definition of base

 (Entry 1 of 3)

1 : a thing or a part on which something rests : bottom, foundation the base of a statue the base of the mountain

2 : a starting place or goal in various games

3 : any of the four stations a runner in baseball must touch in order to score

4 : the main place or starting place of an action or operation The company's base is in New York.

5 : a place where a military force keeps its supplies or from which it starts its operations an air force base

6 : a line or surface of a geometric figure upon which an altitude is or is thought to be constructed base of a triangle

7 : the main substance in a mixture

8 : a number with reference to which a system of numbers is constructed

9 : a chemical substance (as lime or ammonia) that reacts with an acid to form a salt and turns red litmus paper blue


based; basing

Kids Definition of base (Entry 2 of 3)

: to use as a main place of operation or action The company is based in Ohio.

base on or base upon

: to make or form from a starting point It's based on a true story.


baser; basest

Kids Definition of base (Entry 3 of 3)

1 : of low value and not very good in some ways base metals

2 : not honorable “I'll appeal to his baser instincts, of which he has plenty.”— E. B. White, Charlotte's Web


\ˈbās \
plural bases\ ˈbā-​səz \

Medical Definition of base 

1 : that portion of a bodily organ or part by which it is attached to another more central structure of the organism the base of the thumb

2a : the usually inactive ingredient of a preparation serving as the vehicle for the active medicinal preparation the fatty base of an ointment

b : the chief active ingredient of a preparation

called also basis

3a : any of various typically water-soluble and bitter tasting compounds that in solution have a pH greater than 7, are capable of reacting with an acid to form a salt, and are molecules or ions able to take up a proton from an acid or are substances able to give up an unshared pair of electrons to an acid — compare alkali

b : any of the five purine or pyrimidine bases of DNA and RNA that include cytosine, guanine, adenine, thymine, and uracil

4 : freebase

Other Words from base

based \ ˈbāst \ adjective

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