The Jeopardy! round begins when the returning champion selects a clue,
which may be from any position on the game board. The clue is revealed
and read aloud by the host, after which any contestant may ring-in
using a hand-held signaling device. The first contestant to ring-in
successfully is prompted to provide a response to the clue, phrased in
the form of a question.[4] For example, if a contestant were to select
"Presidents for $200", the resulting clue could be "This 'Father of
Our Country' didn't really chop down a cherry tree", to which the
correct response would be "Who is/was George Washington?" (Contestants
are free to phrase the response in the form of any question; the
traditional phrasing of "who is/are" for people or "what is/are" for
things or words is almost always used.) If the contestant responds
correctly, the clue's dollar value is added to the contestant's score,
and they may select a new clue from the board. An incorrect response,
or a failure to respond within five seconds, deducts the clue's value
from the contestant's score and allows the other contestants the
opportunity to ring-in and respond.[4] If no contestant responds
correctly, the host gives the correct response; the "last correct
questioner" chooses the next clue.[8]

From the premiere of the original Jeopardy! until the end of the first
season of the current syndicated series, contestants were allowed to
ring-in as soon as the clue was revealed. Since September 1985,
contestants are required to wait until the clue is read before
ringing-in. To accommodate the rule change, lights were added to the
game board (unseen by home viewers) to signify when it is permissible
for contestants to signal;[9] attempting to signal before the light
goes on locks the contestant out for half of a second.[10] The change
was made to allow the home audience to play along with the show more
easily and to keep an extremely fast contestant from potentially
dominating the game. In pre-1985 episodes, a buzzer would sound when a
contestant signaled; according to Trebek, the buzzer was eliminated
because it was "distracting to the viewers" and sometimes presented a
problem when contestants rang in while Trebek was still reading the
clue.[9] Contestants who are visually impaired or blind are given a
card with the category names printed in Braille before each round
begins, and an audible tone is played after the clue has been read
aloud.

The second round, Double Jeopardy!, features six new categories of
clues. Clue values are doubled from the Jeopardy! round[4] (except in
Super Jeopardy!, where Double Jeopardy! values ranged from 500 to
2,500 points). The contestant with the least money at the end of the
Jeopardy! round makes the first selection in Double Jeopardy!;[8] if
there is a tie, the tied contestant standing at the leftmost lectern
selects first.

A "Daily Double" is hidden behind one clue in the Jeopardy! round, and
behind two in Double Jeopardy![4] The name and inspiration were taken
from a horse racing term.[11] Only the contestant who uncovers a Daily
Double may respond to that clue and need not use his/her signaling
device to do so. Before the clue is revealed, the contestant must
declare a wager, from a minimum of $5 to a maximum of his/her entire
score (known as a "true Daily Double") or the highest clue value
available in the round, whichever is greater.[8] A correct response
adds the value of the wager to the contestant's score, while an
incorrect response deducts it. Whether or not the contestant responds
correctly, he or she maintains control of the board.[8]

During the Jeopardy! round, except in response to the Daily Double
clue, contestants are not penalized for forgetting to phrase their
response in the form of a question, although the host will remind
contestants to watch their phrasing in future responses. In the Double
Jeopardy! round and in the Daily Double in the Jeopardy! round, the
phrasing rule is followed more strictly, with a response not phrased
in the form of a question counting as wrong if it is not re-phrased
immediately. If it is determined that a previous response was wrongly
ruled to be correct or incorrect, the scores are adjusted at the first
available opportunity. If, after a game is over, a ruling change is
made that would have significantly altered the outcome of the game,
the affected contestant(s) are invited back to compete on a future
show.[12]

Contestants who finish Double Jeopardy! with $0 or a negative score
are automatically eliminated from the game at that point and awarded
the third place prize. On at least one episode hosted by Art Fleming,
all three contestants finished Double Jeopardy! with $0 or less, and
as a result, no Final Jeopardy! round was played.[13] During Celebrity
Jeopardy! games, contestants with a $0 or negative score are given
$1,000 for the Final Jeopardy! round.