Appropriations
The legislative act of setting aside specific funds from the federal treasury for a particular purpose. Congress must pass appropriations bills to legally authorize the government to spend money, fulfilling its 'power of the purse.'
The Constitution’s Appropriations Clause (Article I, Section 9) states that “No Money shall be drawn from the Treasury, but in Consequence of Appropriations made by Law” — meaning Congress authorizing a program isn’t enough on its own; a separate appropriations bill must actually fund it. Congress handles this through twelve annual appropriations bills covering different areas of government (defense, labor and health, agriculture, and so on), ordinarily due before the fiscal year begins on October 1.
When Congress fails to pass some or all of these bills on time, agencies without appropriated funding must, under the Antideficiency Act, cease non-essential operations — a government shutdown. The distinction between authorization and appropriation matters enormously in practice: Congress can authorize a program for years while never actually appropriating money for it, effectively leaving it unfunded on paper only.
Common misconception: people often use “authorization” and “appropriation” interchangeably, assuming that once Congress passes a bill creating or extending a program, the money to run it is automatically available. Authorizing legislation sets a program’s legal framework and often a funding ceiling, but the actual dollars only exist once a separate appropriations bill is enacted — a distinction that explains why some authorized federal programs go chronically underfunded or entirely unfunded.