Since it would be terrible for a fellow board member to walk around thinking the NFL rule is the same as the NCAA rule, I have decided to post the corresponding rules and point out the differences - differences every fan should know.
Here is NFL rule 7a:
Note the highlighted requirement of contact by a defensive player in rule 7a.RULE 7 Ball in Play, Dead Ball, Scrimmage
Section 1 Ball in Play
Article 1: Live Ball. After the ball has been declared ready for play, it becomes a live ball when it is legally
snapped or legally kicked (a free kick or fair catch kick). The ball remains dead if it is snapped or kicked
before it is made ready for play.
Section 2 Dead Ball
Article 1: Dead Ball Declared. An official shall declare the ball dead and the down ended:
(a) when a runner is contacted by a defensive player and touches the ground with any part of his body
other than his hands or feet. The ball is dead the instant the runner touches the ground. A runner
touching the ground with his hands or feet while in the grasp of an opponent may continue to
advance; or
There are exceptions to the "when a runner is contacted by a defensive player" requirement. They appear in rules 7c and 7d, not in 7a:
An NFL player can also kneel in the endzone and the ball is dead without contact by a defensive player.(c) when a quarterback immediately drops to his knee (or simulates dropping to his knee) behind the line
of scrimmage; or
(d) when a runner declares himself down by sliding feet first on the ground.
Things are different in the NCAA. Here is the corresponding rule 4.3b
Note the lack of a mandate for contact by a defender.Ball Declared Dead
ARTICLE 3. A live ball becomes dead and an official shall sound his whistle
or declare it dead:
a. When it goes out of bounds other than a kick that scores a field goal after
touching the uprights or crossbar; when a ball carrier is out of bounds;
or when a ball carrier is so held that his forward progress is stopped.
When in question, the ball is dead (A.R. 4-2-1-II).
b. When any part of the ball carrier’s body, except his hand or foot, touches
the ground or when the ball carrier is tackled or otherwise falls and loses
possession of the ball as he contacts the ground with any part of his
body, except his hand or foot
Thus, in the NFL, by rule 7a, contact by a defensive player is required for a ball to be declared dead while this is not so in the NCAA by rule 4.3b.
Note that 4.3b has an exception too:
In other words, in the NCAA (and in the NFL for that matter), the holder on a placekick does not create a dead ball by receiving a snap while on one knee.[Exception: The ball remains alive when
an offensive player has simulated a kick or at the snap is in position to
kick the ball held for a place kick by a teammate. The ball may be kicked,
passed or advanced by rule]