the bottom support of anything; that on which a thing stands or rests:
a metal base for the table.
a fundamental principle or groundwork; foundation; basis:
the base of needed reforms.
the bottom layer or coating, as of makeup or paint.

the distinctively treated portion of a column or pier below the shaft or shafts.
the distinctively treated lowermost portion of any construction, as a monument, exterior wall, etc.

Botany, Zoology.

the part of an organ nearest its point of attachment.
the point of attachment.

the principal element or ingredient of anything, considered as its fundamental part:
face cream with a lanolin base; paint with a lead base.
that from which a commencement, as of action or reckoning, is made; a starting point or point of departure.

any of the four corners of the diamond, especially first, second, or third base.
Compare home plate.
a square canvas sack containing sawdust or some other light material, for marking first, second, or third base.

a starting line or point for runners, racing cars, etc.
(in hockey and other games) the goal.

a fortified or more or less protected area or place from which the operations of an army or an air force proceed.
a supply installation for a large military force.

Geometry. the line or surface forming the part of a figure that is most nearly horizontal or on which it is supposed to stand.

the number that serves as a starting point for a logarithmic or other numerical system.
a collection of subsets of a topological space having the property that every open set in the given topology can be written as the union of sets of the collection.
a collection of neighborhoods of a point such that every neighborhood of the point contains one from the collection.
a collection of sets of a given filter such that every set in the filter is contained in some set in the collection.

Also called base line. Surveying, See under triangulation (def 1).

vehicle (def 10).
Also called carrier. inert matter, used in the preparation of lakes, onto which a coloring compound is precipitated.

Photography. a thin, flexible layer of cellulose triacetate or similar material that holds the light-sensitive film emulsion and other coatings, especially on motion-picture film.

a compound that reacts with an acid to form a salt, as ammonia, calcium hydroxide, or certain nitrogen-containing organic compounds.
the hydroxide of a metal or of an electropositive element or group.
a group or molecule that takes up or accepts protons.
a molecule or ion containing an atom with a free pair of electrons that can be donated to an acid; an electron-pair donor.
any of the purine and pyrimidine compounds found in nucleic acids: the purines adenine and guanine and the pyrimidines cytosine, thymine, and uracil.

Grammar. the part of a complex word, consisting of one or more morphemes, to which derivational or inflectional affixes may be added, as want in unwanted or biolog- in biological.
Compare root1 (def 12), stem1 (def 16).
Linguistics. the component of a generative grammar containing the lexicon and phrase-structure rules that generate the deep structure of sentences.

an electrode or terminal on a transistor other than the emitter or collector electrodes or terminals.
the part of an incandescent lamp or electron tube that includes the terminals for making electrical connection to a circuit or power supply.

Stock Exchange. the level at which a security ceases a decline in price.
Heraldry. the lower part of an escutcheon.
bases, Armor. a tonlet formed of two shaped steel plates assembled side by side.
Jewelry. pavilion (def 6).
in base, Heraldry. in the lower part of an escutcheon.
serving as or forming a base:
The walls will need a base coat and two finishing coats.
to make or form a base or foundation for.
to establish, as a fact or conclusion (usually followed by on or upon):
He based his assumption of her guilt on the fact that she had no alibi.
to place or establish on a base or basis; ground; found (usually followed by on or upon):
Our plan is based on a rising economy.
to station, place, or situate (usually followed by at or on):
He is based at Fort Benning. The squadron is based on a carrier.
to have a basis; be based (usually followed by on or upon):
Fluctuating prices usually base on a fickle public’s demand.
to have or maintain a base:
I believe they had based on Greenland at one time.
get to first base. first base (def 2).
off base,

Baseball. not touching a base:
The pitcher caught him off base and, after a quick throw, he was put out by the second baseman.
Informal. badly mistaken:
The police were way off base when they tried to accuse her of the theft.

on base, Baseball. having reached a base or bases:
Two men are on base.
touch base with, to make contact with:
They’ve touched base with every political group on campus.
morally low; without estimable personal qualities; dishonorable; meanspirited; selfish; cowardly.
of little or no value; worthless:
hastily composed of base materials.
debased or counterfeit:
an attempt to eliminate the base coinage.
characteristic of or befitting an inferior person or thing.
of illegitimate birth.
not classical or refined:
base language.
Old English Law. held by tenure less than freehold in return for a service viewed as somewhat demeaning to the tenant.

of humble origin or station.
of small height.
low in place, position, or degree:
base servitude.

Obsolete. deep or grave in sound; bass:
the base tones of a piano.
Music Obsolete, bass1 (defs 3, 4).
a technique for establishing the distance between any two points, or the relative position of two or more points, by using such points as vertices of a triangle or series of triangles, such that each triangle has a side of known or measurable length (base or base line) that permits the size of the angles of the triangle and the length of its other two sides to be established by observations taken either upon or from the two ends of the base line.
the triangles thus formed and measured.
Contemporary Examples

Beholden to a base that, like a capricious autocrat, will turn against them at the slightest provocation.
Ted Cruz is Still Not Here to Make Friends Jamelle Bouie February 25, 2014

Earlier this year, the chief of the CIA base in Benghazi won an intelligence award for his performance there.
Up to Speed: 5 Things You Need to Know About Benghazi Eli Lake September 10, 2013

Selling the case to Moscow for building that base is likely to prove Mission Impossible.
Cold War II? Martin Sieff November 16, 2008

From his British base, Altaf runs the MQM as a private party with him in complete control.
Altaf Hussain Finally Arrested in London; Can His MQM Be Neutralized? Bruce Riedel June 2, 2014

It also plays well with the Republican base to beat up on the liberal media.
The GOP’s Candy Strategy Howard Kurtz October 16, 2012

Historical Examples

In some of the swamps at the base of the mountain grows Limnorchis leucostachys.
The Mountain that was ‘God’ John H. Williams

A stream of water, pure as crystal, flowed along the path, from the summit to the base.
Philothea Lydia Maria Child

The road we followed skirted the base of one range of hills.
The Creed of the Old South 1865-1915 Basil L. Gildersleeve

It comes out of a subconsciousness in which death and not life is the base.
The Conquest of Fear Basil King

He could not be so base, my boy,” said his mother, “when he owes you his life.
A Dog with a Bad Name Talbot Baines Reed

the bottom or supporting part of anything
the fundamental or underlying principle or part, as of an idea, system, or organization; basis

a centre of operations, organization, or supply: the climbers made a base at 8000 feet
(as modifier): base camp

a centre from which military activities are coordinated
anything from which a process, as of measurement, action, or thought, is or may be begun; starting point: the new discovery became the base for further research
the main ingredient of a mixture: to use rice as a base in cookery
a chemical compound that combines with an acid to form a salt and water. A solution of a base in water turns litmus paper blue, produces hydroxyl ions, and has a pH greater than 7. Bases are metal oxides or hydroxides or amines See also Lewis base
(biochem) any of the nitrogen-containing constituents of nucleic acids: adenine, thymine (in DNA), uracil (in RNA), guanine, or cytosine
a medium such as oil or water in which the pigment is dispersed in paints, inks, etc; vehicle
the inorganic material on which the dye is absorbed in lake pigments; carrier

the part of an organ nearest to its point of attachment
the point of attachment of an organ or part

the bottommost layer or part of anything

the lowest division of a building or structure
the lower part of a column or pier

another word for baseline (sense 2)
the lower side or face of a geometric construction

the number of distinct single-digit numbers in a counting system, and so the number represented as 10 in a place-value system: the binary system has two digits, 0 and 1, and 10 to base two represents 2 See place-value
(of a logarithm or exponential) the number whose powers are expressed: since 1000 = 10³, the logarithm of 1000 to base 10 is 3
(of a mathematical structure) a substructure from which the given system can be generated
the initial instance from which a generalization is proven by mathematical induction

(logic, maths) Also called base clause. the initial element of a recursive definition, that defines the first element of the infinite sequence generated thereby

a root or stem
See base component

(electronics) the region in a transistor between the emitter and collector
(photog) the glass, paper, or cellulose-ester film that supports the sensitized emulsion with which it is coated
(heraldry) the lower part of the shield
(jewellery) the quality factor used in pricing natural pearls
a starting or finishing point in any of various games
(baseball) any of the four corners of the diamond, which runners have to reach in order to score
the main source of a certain commodity or element: a customer base, their fan base
(US & Canadian, informal) get to first base, to accomplish the first stage in a project or a series of objectives
(US & Canadian, informal) off base, wrong or badly mistaken
touch base, to make contact
(transitive foll by on or upon) to use as a basis (for); found (on): your criticisms are based on ignorance
often foll by at or in. to station, post, or place (a person or oneself)
devoid of honour or morality; ignoble; contemptible
of inferior quality or value
debased; alloyed; counterfeit: base currency
(English history)

(of land tenure) held by villein or other ignoble service
holding land by villein or other ignoble service

(archaic) born of humble parents; plebeian
(archaic) illegitimate
adjective, noun
(music) an obsolete spelling of bass1
a method of surveying in which an area is divided into triangles, one side (the base line) and all angles of which are measured and the lengths of the other lines calculated trigonometrically
the network of triangles so formed
the fixing of an unknown point, as in navigation, by making it one vertex of a triangle, the other two being known
(chess) a key manoeuvre in the endgame in which the king moves thrice in a triangular path to leave the opposing king with the move and at a disadvantage

See base number

See trilateration

“bottom, foundation, pedestal,” early 14c., from Old French bas “depth” (12c.), from Latin basis “foundation,” from Greek basis “step, pedestal,” from bainein “to step” (see come). The military sense is from 1860. The chemical sense (1810) was introduced in French 1754 by French chemist Guillaume-François Rouelle (1703-1770). Sporting sense of “starting point” ia from 1690s, also “destination of a runner” (1812). As a “safe” spot in a tag-like game, suggested from mid-15c. (as the name of the game later called prisoner’s base).

late 14c., “low, of little height,” from Old French bas “low, lowly, mean,” from Late Latin bassus “thick, stumpy, low” (used only as a cognomen in classical Latin, humilis being there the usual word for “low in stature or position”), possibly from Oscan, or Celtic, or related to Greek basson, comparative of bathys “deep.” Figurative sense of “low in the moral scale” is first attested 1530s in English, earlier “servile” (1520s). Base metals (c.1600) were worthless in contrast to noble or precious metals.

“to place on a foundation,” 1841, from base (n.). Related: Based; basing.

1818, from Medieval Latin triangulationem (mid-12c., nominative triangulatio), noun of action from Latin *triangulare, from triangulum (see triangle).

base (bās)

The part of an organ nearest its point of attachment.

A fundamental ingredient; a chief constituent of a mixture.

Any of a large class of compounds, including the hydroxides and oxides of metals, having a bitter taste, a slippery solution, the capacity to turn litmus blue, and to react with acids to form salts.

A molecular or ionic substance capable of combining with a proton to form a new substance. Also called Brønsted base.

A nitrogen-containing organic compound that combines in such a manner.

A substance that provides a pair of electrons for a covalent bond with an acid.



Any of a class of compounds that form hydroxyl ions (OH) when dissolved in water, and whose aqueous solutions react with acids to form salts. Bases turn red litmus paper blue and have a pH greater than 7. Their aqueous solutions have a bitter taste. Compare acid.

See nitrogen base.

The side or face of a geometric figure to which an altitude is or is thought to be drawn. The base can be, but is not always, the bottom part of the figure.

The number that is raised to various powers to generate the principal counting units of a number system. The base of the decimal system, for example, is 10.

The number that is raised to a particular power in a given mathematical expression. In the expression an, a is the base.


The side or face of a geometric figure to which an altitude is or is thought to be drawn. The base can be, but is not always, the bottom part of the figure.

The number that is raised to various powers to generate the principal counting units of a number system. The base of the decimal system, for example, is 10.

The number that is raised to a particular power in a given mathematical expression. In the expression an, a is the base.

A method of determining the relative positions of points in space by measuring the distances, and sometimes angles, between those points and other reference points whose positions are known. Triangulation often involves the use of trigonometry. It is commonly used in the navigation of aircraft and boats, and is the method used in the Global Positioning System , in which the reference points are satellites.

Any of a number of bitter-tasting, caustic materials. Technically, a material that produces negative ions in solution. A base is the opposite of an acid and has a pH of 7 to 14. A given amount of a base added to the same amount of an acid neutralizes the acid; water and a salt are produced. Alkalis are bases; ammonia is a common base.

Related Terms

get to first base, off base, off one’s base, touch base with someone


get to first base
off base
touch base


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