What is the difference amongst prison, jail, and the penitentiary?

Primarily, the difference is that a jail is used by local jurisdictions such as counties and cities to confine people for short periods of time. A prison, or penitentiary, is administered by the state, and is used to house convicted criminals for periods of much longer duration. Both are part of a larger penal system which includes other aspects of criminal justice such as courts, law enforcement, and crime labs.

Jail--Short Term
Prison--Long Term

http://www.wisegeek.com/what-is-the-difference-between-a-jail-and-a-prison.htm

--- JAIL : prison, esp. one for the detention of persons awaiting trial or convicted of minor offenses.
--- PRISON : a building for the confinement of persons held while awaiting trial, persons sentenced after conviction
--- PENITENTIARY : a place for imprisonment, reformatory discipline, or punishment, esp. a prison maintained in the U.S. by a state or the federal government for serious offenders.

http://dictionary.reference.com/browse/jail
http://dictionary.reference.com/browse/prison
http://dictionary.reference.com/search?q=penitentiary

You can be sentenced for up to two years (most jurisdictions) in a County Jail. The way this is done is by a "24 Month" sentence rather than a "2 year" sentence. It is a loop hole in the Penal System that is exploited to keep the Money Coming in to a County facility. Federal, State and Local funds pay for inmates. It Is ALL ABOUT THE MONEY and how to keep it coming in.

I know you've had your question answered, but to open it up internationally, prison and jail are simply synonyms in the UK.

Think short-term and long-term.

Jails are most often run by sheriffs and/or local governments and are designed to hold individuals awaiting trial or a serving short sentences.

Prisons are operated by state governments and the Federal Bureau of Prisons (BOP) and are designed to hold individuals convicted of crimes.

Jails operate work release programs, boot camps, and other specialized services. They try to address educational needs, substance abuse needs, and vocational needs while managing inmate behavior. Inmate idleness contributes to management problems.

State prison systems operate halfway houses, work release centers and community restitution centers - all considered medium or minimum custody. Inmates assigned to such facilities are usually reaching the end of their sentences.


http://cleminfostrategies.com/whats-the-difference-between-prison-and-jail/

from personal experience I must agree with igotmeajd
it irks me to watch David Letterman talk about different celebs going to prison I know he's going for the humor but... to me it shows ignorance when one knows better but consistantly does it wrong

"- jail is not as bad as prison."

It's worse, actually, just not as serious.

I know that doesn't make sense, but the following Wiki link does a great job of explaining it. People who know they're going to get a long sentence greatly look forward to getting out of the usually over-crowded and dangerous jail into a "home" of sorts in a more amenable prison. Not that prison's fun, just that jail's worse, even though on your record having been in a prison looks worse.

"As a result, many jails operate their booking and receiving units at a relatively high level of correctional security, and also witness a disproportionately large amount of violence and disciplinary problems as compared to mainline facilities."

https://en.wikipedia.org/wiki/Jail

Calaboose, hoosegow, slammer, clink, and many more are used simply as synonyms for prison or penitentiary.

Penitentiary: a public institution in which offenders against the law are confined for detention or punishment; specifically : a state or federal prison in the United States
Prison: A correctional facility prison, jail is a facility in which inmates are forcibly confined and denied a variety of freedoms under the authority of the state as a form of punishment.
http://www.merriam-webster.com/dictionary/penitentiary