base

1 of 4

noun

ˈbās 

plural bases ˈbā-səz 

1

a

: the bottom of something considered as its support : foundation

the base of the mountain

the lamp's heavy base

b

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

c 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)

d 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

2

a

: 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

3

a

: 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 base

the band's fan base

But 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

a

: the starting point or line for an action or undertaking

He 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)

: a permanent military installation

a naval base

The troops were ordered back to base.

(2)

: the place from which a military force draws supplies

(3)

: a place where military operations begin

d

linguistics : root sense 6

"Leave" is the base of the verb "left."

e mathematics

(1)

: a number (such as 5 in 5^6.44 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.

5

a

: any one of the four stations at the corners of a baseball or softball infield

allowing the batter to reach base

b

in various games : the starting place or goal

c

: a point to be considered

His opening remarks touched every base.

6

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, turn litmus blue, 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

Baking soda is a common household base.

b

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

7

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

8

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

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

baseless

ˈbā-sləs 

adjective

Illustration of base

• 1 upper torus
• 2 scotia
• 3 lower torus
• 4 plinth
• 5 shaft
• 6 fillets

see also cover all the bases, off base, touch all the bases

base

2 of 4

verb

based; basing

transitive verb

1

: 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 information

a story based upon real-life events

2

: 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

base

3 of 4

adjective (1)

1

a

: 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

2

a

: 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 sense 5

b

: containing a larger than usual proportion of base metals

base silver denarii

3

feudalism

a

: resembling a villein : servile

a base tenant

b

: held by villenage

base tenure

4

archaic : of little height

… the cedar stoops not to the base shrub's foot …

—Shakespeare

5

archaic : baseborn

… base in kind and born to be a slave.

—William Cowper

6

obsolete : low in place or position

… fall to the base earth from the firmament!

—Shakespeare

7

obsolete : bass

basely adverb

baseness noun

base

4 of 4

adjective (2)

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

Synonyms of base

Noun

• basis
• foundation
• bedrock
• cornerstone

Verb

• ground
• predicate
• rest

Adjective (1)

• vile
• dirty
• nasty
• immoral
• low
• corrupt
• vicious
• ignoble
• bad
• detestable
• mean
• paltry
• cruel
• low-down
• ignominious

Choose the Right Synonym for base

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

Noun

their base obedience to every unprincipled action ordered by their leader

the army's base of attack was kept top secret until the battle began

Verb

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

Recent Examples on the Web

Noun

Alonso's absence is a much bigger issue for the Mets, as none of the remaining free agents at firs base provide as much offensive upside as the five-time All-Star. —Aaron Coloma, MSNBC Newsweek, 12 Dec. 2025

While Sons usually adds 2-3 inches deep of mulch around the plant's base. —Lauren David, Southern Living, 12 Dec. 2025

Verb

Additionally, the first knockout round is the Round of 32, which means the top two teams from each group advance past the group stages and the eight best third-place teams move on, based on points, goal differential, goals scored, discipline (card points) and FIFA ranking. —Chris Biderman, Sacbee.com, 7 Dec. 2025

The cruise line — whose parent company is Carnival Corporation — is based in Germany. —Natalia Senanayake, PEOPLE, 6 Dec. 2025

Adjective

The Unit-1 has a base weight of 780 lb (354 kg) and a GVWR of 2,000 lb (907 kg) delivered by a Timbren Axle-Less suspension. —New Atlas, 7 Dec. 2025

The developer is also utilizing the state density bonus law and plans to offer 15% of the base number of units to very low-income households and another 15% to moderate-income households. —Devan Patel, Mercury News, 3 Dec. 2025

Word History

Etymology

Noun

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

Verb

verbal derivative of base entry 1

Adjective (1)

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

First Known Use

Noun

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

Verb

1587, in the meaning defined at sense 2

Adjective (1)

14th century, in the meaning defined at sense 4

Adjective (2)

1734, in the meaning defined at sense 1

Phrases Containing base

• air base
• base angle
• base exchange
• base hit
• base of operations
• base on balls
• base pair
• base path
• base pay
• base price
• base runner
• base stealer
• base unit
• customer base
• extra-base hit
• fan base
• first base
• get to first base
• home base
• loosely base on
• on base
• on-base percentage
• power base
• prisoner's base
• second base
• tax base
• third base
• touch base
• zero-base

Rhymes for base

• ace
• brace
• case
• chace
• dace
• face
• grace
• lace
• mace
• pace
• place
• race

Kids Definition

base

1 of 3 noun

ˈbās 

plural bases ˈbā-səz 

1

a

: a thing or part on which something rests : bottom, foundation

the base of a lamp

b

: the part of a plant or animal structure by which it is attached to another more central structure

the base of the thumb

c

: one of the lines or flat surfaces of a geometric figure from which an altitude is or can be constructed

bases of a trapezoid

especially : one on which the figure stands

base of a triangle

2

: a main ingredient

paint having a water base

3

: a fundamental part : basis

4

a

: the place from which a start is made

b

: a line in a survey that is used to calculate distances or positions

c

: a place where a military force keeps its supplies or from which it starts its operations

naval base

air base

d

: a number equal to the number of units that would be equivalent to one in the next higher place in a given number system

in base 10 it takes 10 ones in the units place to equal a one in the tens place

also : a system of writing numbers using a given base

convert base 10 to base 2

e

: root entry 1 sense 5

5

a

: the starting place or goal in various games

b

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

6

: any of various compounds that react with an acid to form a salt, have a bitter taste, and turn red litmus paper blue

7

: 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% multiply the base 90 by .10

based adjective

baseless

ˈbās-ləs 

adjective

base

2 of 3 verb

based; basing

1

: to make, form, or serve as a base for

2

: to use as a base or basis for : establish

base

3 of 3 adjective

1

a

: being of low value and having less desirable properties when compared with something else

a base metal such as iron

b

: containing more than the usual amount of base metals

2

: not honorable or moral : mean

base conduct

basely adverb

baseness noun

Medical Definition

base

noun

ˈbās 

plural bases ˈbā-səz 

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

2

a

: 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

3

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 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

based

ˈbāst 

adjective