The Collaborative International Dictionary of English v.0.48:

agency \a"gen*cy\ ([=a]"jen*s[y^]), n.; pl. Agencies
   ([=a]"jen*s[i^]z). [agentia, fr. L. agens, agentis: cf. F.
   agence. See Agent.]
   1. The faculty of acting or of exerting power; the state of
      being in action; action; instrumentality.
      [1913 Webster]

            The superintendence and agency of Providence in the
            natural world.                        --Woodward.
      [1913 Webster]

   2. The office of an agent, or factor; the relation between a
      principal and his agent; business of one intrusted with
      the concerns of another.
      [1913 Webster]

   3. The place of business of an agent.
      [1913 Webster]

   4. An organization or business that provides some service,
      primarily for other organizations; as, an advertising
      agency.
      [PJC]

   5. An administrative division of a government; as, a state
      welfare agency; a motor vehicle agency; the Environmental
      Protection Agency (EPA); the Federal Emergency Management
      Agency (FEMA).
      [PJC]

   Syn: Action; operation; efficiency; management.
        [1913 Webster]

WordNet (r) 3.0 (2006):

agency
    n 1: an administrative unit of government; "the Central
         Intelligence Agency"; "the Census Bureau"; "Office of
         Management and Budget"; "Tennessee Valley Authority" [syn:
         agency, federal agency, government agency, bureau,
         office, authority]
    2: a business that serves other businesses
    3: the state of being in action or exerting power; "the agency
       of providence"; "she has free agency"
    4: the state of serving as an official and authorized delegate
       or agent [syn: representation, delegacy, agency]
    5: how a result is obtained or an end is achieved; "a means of
       control"; "an example is the best agency of instruction";
       "the true way to success" [syn: means, agency, way]

Moby Thesaurus II by Grady Ward, 1.0:

166 Moby Thesaurus words for "agency":
   action, activity, agent, agentship, antecedent, assignment,
   atelier, authority, authorization, barbershop, barter, bartering,
   beauty parlor, beauty shop, bench, brevet, brokerage, butcher shop,
   buying and selling, care, cause, change, channel, charge,
   commission, commissioning, commitment, commutation, company,
   concern, conduct, consignment, corporation, cure, dealing,
   delegated authority, delegation, deputation, deputyship, desk,
   determinant, device, devolution, devolvement, direction,
   displacement, doing business, driving, embassy, empowerment,
   energy, entrusting, entrustment, errand, establishment, exchange,
   execution, executorship, exequatur, exercise, expedient, facility,
   factorship, firm, force, full power, functioning, gear,
   give-and-take, going between, handling, horse trading, house,
   installation, institution, instrumentality, instrumentation,
   intercession, interchange, intermediation, intervention, jobbing,
   jurisdiction, legation, license, lieutenancy, loft, machinery,
   management, mandate, manipulation, means, mechanism, mediation,
   medium, merchandising, ministry, mission, occupation, office,
   operancy, operation, organ, organization, parlor, performance,
   performing, plenipotentiary power, power, power of attorney,
   power to act, practice, procuration, proxy, purview, quid pro quo,
   recourse, regency, regentship, replacement, representation, resort,
   responsibility, retailing, running, service, shop, steering,
   studio, subrogation, substitution, supersedence, superseding,
   supersedure, supersession, supplantation, supplanting,
   supplantment, swapping, sweatshop, switch, task, tit for tat,
   trade, trading, trafficking, trust, trusteeship, vehicle,
   vicarious authority, vicariousness, warrant, wheeling and dealing,
   wholesaling, work, work site, work space, workbench, workhouse,
   working, working space, workings, workplace, workroom, workshop,
   worktable



Bouvier's Law Dictionary, Revised 6th Ed (1856):

AGENCY, contracts. An agreement, express, or implied, by which one of the
parties, called the principal, confides to the other, denominated the agent,
the management of some business; to be transacted in his name, or on his
account, and by which the agent assumes to do the business and to render an
account of it. As a general rule, whatever a man do by himself, except in
virtue of a delegated authority, he may do by an agent. Combee's Case, 9 Co.
75.  Hence the maxim qui facit per alium facit per se.
     2. When the agency express, it is created either by deed, or in writing
not by deed, or verbally without writing. 3 Chit. Com. Law 104; 9 Ves. 250;
11 Mass. Rep. 27; Ib. 97, 288; 1 Binn. R. 450. When the agency is not
express, it may be inferred from the relation of the parties and the nature
of the employment, without any proof of any express appointment. 1 Wash. R.
19; 16 East, R. 400; 5 Day's R. 556.
     3. The agency must be antecedently given, or subsequently adopted; and
in the latter case there must be an act of recognition, or an acquiescence
in the act of the agent, from which a recognition may be fairly implied. 9
Cranch, 153, 161; 26 Wend. 193, 226; 6 Man. & Gr. 236, 242; 1 Hare & Wall.
Sel. Dec. 420; 2 Kent, Com. 478; Paley on Agency; Livermore on Agency.
     4. An agency may be dissolved in two ways - 1, by the act of the
principal or the agent; 2, by operation of law.
     5.-1. The agency may be dissolved by the act of one of the parties.
1st. As a general rule, it may be laid down that the principal has a right
to revoke the powers which he has given; but this is subject to some
exception, of which the following are examples. When the principal has
expressly stipulated that the authority shall be irrevocable, and the agent
has an interest in its execution; it is to be observed, however, that
although there may be an express agreement not to revoke, yet if the agent
has no interest in its execution, and there is no consideration for the
agreement, it will be considered a nude pact, and the authority may be
revoked. But when an authority or power is coupled with an interest, or when
it is given for a valuable consideration, or when it is a part of a
security, then, unless there is an express stipulation that it shall be
revocable, it cannot be revoked, whether it be expressed on the face of the
instrument giving the authority, that it be so, or not. Story on Ag. 477;
Smith on Merc. L. 71; 2 Liv. on Ag. 308; Paley on Ag. by Lloyd, 184; 3 Chit.
Com. f. 223; 2 Mason's R. 244; Id. 342; 8 Wheat. R. 170; 1 Pet. R. 1; 2
Kent, Com. 643, 3d edit.; Story on Bailm. Sec. 209; 2 Esp. R. 665; 3 Barnw.
& Cressw. 842; 10 Barnw. & Cressw. 731; 2 Story, Eq. Jur. Sec. 1041, 1042,
1043
     6.-2. The agency may be determined by the renunciation of the agent.
If  the renunciation be made after it has been partly executed, the agent by
renouncing it, becomes liable for the damages which may thereby be sustained
by his principal. Story on Ag. Sec. 478; Story on Bailm. Sec. 436; Jones on
Bailm. 101; 4 John r. 84.
     7.-2 The agency is revoked by operation of law in the following
cases: 1st. When the agency terminates by the expiration of the period,
during which it was to exist, and to have effect; as, if an agency be
created to endure a year, or till the happening of a contingency, it becomes
extinct at the end or on the happening of the contingency.
     8.-2. When a change of condition, or of state, produces an incapacity
in either party; as, if the principal, being a woman, marry, this would be a
revocation, because the power of creating an agent is founded on the right
of the principal to do the business himself, and a married woman has no such
power. For the same reason, when the principal becomes insane, the agency is

ipso facto revoked. 8 Wheat. R. 174, 201 to 204; Story on Ag. Sec. 481;
Story on Bailm. Sec. 206. 2 Liv. on Ag. 307. The incapacity of the agent
also amounts to a  revocation in law, as in case of insanity, and the like,
which renders an agent altogether incompetent, but the rule does not
reciprocally apply in its full extent. For instance, an infant or a married
woman may in some cases be agents, although they cannot act for themselves.
Co. Litt. 52a.
     9.-3. The death of either principal or agent revokes the agency,
unless in cases where the agent has an interest in the thing actually vested
in the agent. 8 Wheat. R. 174; Story on Ag. Sec. 486 to 499; 2 Greenl. R.
14, 18; but see 4 W. & S. 282; 1 Hare & Wall. Sel. Dec. 415.
     10.-4. The agency is revoked in law, by the extinction of the
subject-matter of the agency, or of the principal's power over it, or by the
complete execution of the trust. Story on Bailm. Sec. 207, Vide generally, 1
Hare & Wall. Sel. Dec. 384, 422; Pal. on Ag.; Story on Ag.; Liv. on Ag.; 2
Bouv. Inst. n. 1269-1382.



U.S. Gazetteer Places (2000):

Agency, MT -- U.S. Census Designated Place in Montana
   Population (2000):    324
   Housing Units (2000): 90
   Land area (2000):     8.577370 sq. miles (22.215286 sq. km)
   Water area (2000):    0.007082 sq. miles (0.018342 sq. km)
   Total area (2000):    8.584452 sq. miles (22.233628 sq. km)
   FIPS code:            00587
   Located within:       Montana (MT), FIPS 30
   Location:             48.257148 N, 109.772875 W
   ZIP Codes (1990):
   Note: some ZIP codes may be omitted esp. for suburbs.
   Headwords:
    Agency, MT
    Agency


U.S. Gazetteer Places (2000):

Agency, IA -- U.S. city in Iowa
   Population (2000):    622
   Housing Units (2000): 286
   Land area (2000):     0.578829 sq. miles (1.499159 sq. km)
   Water area (2000):    0.000000 sq. miles (0.000000 sq. km)
   Total area (2000):    0.578829 sq. miles (1.499159 sq. km)
   FIPS code:            00640
   Located within:       Iowa (IA), FIPS 19
   Location:             40.995432 N, 92.307532 W
   ZIP Codes (1990):     52530
   Note: some ZIP codes may be omitted esp. for suburbs.
   Headwords:
    Agency, IA
    Agency


U.S. Gazetteer Places (2000):

Agency, MO -- U.S. village in Missouri
   Population (2000):    599
   Housing Units (2000): 222
   Land area (2000):     1.936828 sq. miles (5.016361 sq. km)
   Water area (2000):    0.000000 sq. miles (0.000000 sq. km)
   Total area (2000):    1.936828 sq. miles (5.016361 sq. km)
   FIPS code:            00298
   Located within:       Missouri (MO), FIPS 29
   Location:             39.648739 N, 94.744418 W
   ZIP Codes (1990):     64401
   Note: some ZIP codes may be omitted esp. for suburbs.
   Headwords:
    Agency, MO
    Agency