The rules that use the vocabulary item "four" are:

<craft_message>

fox four

<point_id-entry_point>

bugs four

<point_id-craft_landing_zone>

bugs four

<hour>

four

oh four

zero four

one four

<point_id-checkpoint>

bugs four

<point_id>

bugs four

<point_id-waypoint>

bugs four

<digit-not_zero>

four

<airspace_nom>

c v o a four

<air_formation_nom>

fluid four

spread four

<point_id-cap>

bugs four

<digit-pl>

four

<scale_number-gapsout_null-gapsin_null>

four hundred

four hundred fifty

four thousand

four thousand five hundred

four hundred thousand

four hundred fifty thousand

<air_call_sign_designator>

dash four

<point_id-point_id_type_none>

bugs four

<digit_not_one>

four

<digit_zero_to_five>

four

<point_id-debark_point>

bugs four

<digit_zero_to_seven>

four

<controller>

coyote one four alpha

<digit>

four

<digit-not_zero-pl>

four

<point_id-embark_point>

bugs four

<point_id-bullseye>

bugs four

<point_id-coordination_point>

bugs four

<point_id-base_of_fire>

bugs four

<up_to_six>

four

<point_id-initial_point>

bugs four

<digit_one_to_eight>

four

<controller-recursive>

coyote one four alpha

<point_id-holding_point>

bugs four

<point_id-landing_zone>

bugs four

<point_id-homebase>

bugs four