The feature Number is pertinent to all the finite forms and,
among the non-finite forms, to the participles.
This feature is in combination with the values 1, 2 et 3 of the
feature Person.
This feature doesn't apply to infinitive and gerund.
The feature number applies in combination with the feature gender to
past participles.
For imperative (impr),
the value 2 of person combines with the two values, sing and plur.
For some defective verbs not the all values are realized.