Laws of Cricket 1980 Code - Law 18
1. A Run
The score shall be reckoned by runs. A run is scored:
a. So often as the Batsmen, after a hit or at any time while the ball is in play, shall have crossed and made good their ground from end to end.
b. When a boundary is scored. See Law 19 (Boundaries).
c. When penalty runs are awarded. See 6 below.
2. Short Runs
a. If either batsman runs a short run, the umpire shall call and signal "one short" as soon as the ball becomes dead and that run shall not be scored. A run is short if a batsman fails to make good his ground on turning for a further run.
b. Although a short run shortens the succeeding one, the latter, if completed shall count.
c. If either or both batsmen deliberately run short the umpire shall, as soon as he sees that the fielding side have no chance of dismissing either batsman, call and signal "dead ball" and disallow any runs attempted or previously scored. The batsmen shall return to their original ends.
d. If both batsmen run short in one and the same run, only one run shall be deducted.
e. Only if three or more runs are attempted can more than one be short and then, subject to (c) and (d) above, all runs so called shall be disallowed. If there has been more than one short run the Umpires shall instruct the scorers as to the number of runs disallowed.
3. Striker Caught
If the striker is caught, no run shall be scored.
4. Batsman Run Out
If a batsman is run out, only that run which was being attempted shall not be scored. If, however, an injured striker himself is run out no runs shall be scored. See Law 2.7 (Transgression of the Laws by an Injured Batsman or Runner).
5. Batsman Obstructing the Field
If a batsman is out Obstructing the Field, any runs completed before the obstruction occurs shall be scored unless such obstruction prevents a catch being made in which case no runs shall be scored.
6. Runs Scored for Penalties
Runs shall be scored for penalties under Law 20 (Lost Ball), Law 24 (No Ball), Law 25 (Wide Ball), Law 41.1 (Fielding the Ball) and for boundary allowances under Law 19 (Boundaries).
7. Batsman Returning to Wicket he has Left
If, while the ball is in play, the batsmen have crossed in running, neither shall return to the wicket he has left even though a short run has been called or no run has been scored as in the case of a catch. Batsmen, however, shall return to the wickets they originally left in the cases of a boundary and of any disallowance of runs and of an injured batsman being, himself, runout. See Law 2.7 (Transgression of the Laws by an Injured Batsman or Runner).
Note
1. Short Run
A striker taking stance in front of his popping crease may run from that point without penalty.
Reproduction of the Laws of Cricket is by kind permission of Marylebone Cricket Club