Rule established by the Laws and Ethics Committee of the EBU, stating that the minimum agreeable standard for an opening suit bid at the one- level is that the sum of the number of high-card points and the lengths of the two longest suits must total at least nineteen.
For example:
With 9 high-card points and two 5-card suits, this hand would be minimally acceptable under the Rule of Nineteen for an opening bid (9+5+5).
Note that this Rule does not suggest that weak hands of this type justify a sensible opening bid (especially here when the singleton king may be worth less than 3 points), but rather that bidding with a lower total than 19 would constitute a psyche.
Most players use either the rule of 20 or a more sophisticated rule that also takes account of the hand’s defensive potential.