Definitions

Axis Point:
One of two points located on opposite poles marking the end points of the axis of rotation.
Axis Tilt:
The vertical angle between the axis of rotation and the surface of the lane.
Axis Rotation:
The angle between the axis of rotation and the direction in which the bowling ball is traveling.
Balance Hole:
A hole drilled into the bowling ball to alter either the static or dynamic mass distribution in a bowling ball. A ball driller can use this type of hole to make a bowling ball comply with USBC specifications and/or to alter the ball dynamics to either increase or decrease hook characteristics.
Ball Speed:
Slower - Initial velocity is less than 17mph.
Medium - Initial velocity is between 17 mph and 19 mph.
Faster - Initial velocity is greater than 19 mph.

There is a formula to calculate a player's velocity:
1. Determine the elapsed time (in seconds, i.e. 2.52) from the moment of a player's release to the moment of impact on the pins.
2. Divide this number into 40.91 (i.e. 40.91/2.52 = 16.23 mph).
Breakpoint:
The point on the lane where the ball has its strongest change in direction.
Carry-down:
Refers to the oil that travels to the previously dry backends. This condition results in less overall hook.
Center Line:
A vertical line that extends from the center of the thumb hole through the point between the finger holes.
Center of Gravity (CG):
The marking on the surface of the bowling ball about which the weight of the bowling ball is equally distributed in any direction. The true center of gravity of the bowling ball will be somewhere between this mark and the center of the ball.
Core (aka: weight block):
The large, round inner portion of a three piece bowling ball. This area consists of the filler material and may have other high-density materials for dynamic purposes.
Core Torque:
The mass distribution within the arms created by the core (or weight block). Core torque is an assigned value of the ball's ability to combat rollout, the complete loss of axis tilt. High torque balls are more effective than lower torque balls at delaying "rollout". High torque balls will tend to react more violently on the backend than lower torque balls, which roll even, displaying a more predictable transition from skid to roll.
Coverstock:
The outer shell of bowling balls, which can be constructed with a variety of materials such as polyester, rubber, urethane and reactive urethane.
D-Scale:
Refers to an instrument (Durometer) used to measure the hardness of the coverstock of a bowling ball.
Delivery Dynamics:
The combination of velocity, loft, rev rate, axis tilt and the axis of rotation of the bowling ball at the moment of release.
The difference between the Radius of Gyration (RG) of the x-axis and the y-axis of a bowling ball. The maximum currently allowed by the USBC is 0.060.
Dull:
The surface of a bowling ball appearing without reflection (synonym - sanded).
Flare:
The migration of the ball's spin axis. This is created by a combination of the layout of the ball and the dynamics of the core of the ball.
Flare Potential:
The maximum amount that the axis of a bowling ball can migrate given the construction of the ball provided that the bowler has a maximum power release. Flare potential can also be used to indicate which balls will be better suited for oily conditions (high flare balls) and which balls will be better suited for dryer lane conditions (low flare balls).
Friction:
The energy released upon the bowling ball contacting the lane surface causing the transition from skid to roll.
Grit:
Pertaining to the texture of the surface of the ball, whether polished or sanded.
The portion of the lane, which extends from the foul line, past the arrows, and to the pine. Usually, this is assumed to be the first 20 feet of the lane.
Hook Potential:
A scale used to describe the total amount of hook possible form a bowling ball. The amount of hook a bowler will obtain with any given bowling ball will depend on the layout used and the bowler's delivery dynamics.
Intermediate Differential:
The difference between the radius of gyration of the y-axis of the ball and the z-axis. Bowling balls with asymmetrical cores will have a larger intermediate differential than balls with symmetrical cores.
Lane Oil / Conditioner:
Substance that was developed to reduce friction between the ball and the lane, with the ultimate goal of protecting the lane surface. It also allows the ball to skid down to its desired roll and hook point, and its placement can greatly affect scores.
Length:
An evaluation of how far a ball will travel before it begins to hook. Length does not include skid caused by lane conditioner, additional fine sanding, or the use of polishes.
Leverage Point:
The position located 3-3/8" from the bowler's positive axis point (PAP). Positioning the mass (or pin) of a bowling ball on this point creates the most track flare and over all hook of a bowling ball.
Loft:
The distance from the foul line that the ball impacts the lane.
Mass Bias:
A modification of the core that places the mass of the core away from the x-axis of the ball. The mass bias of a bowling ball is not always in the same location as the preferred spin axis.
Midlane:
This is the middle part of the lane past the heads (1 st 20 feet of the lane) and before the backends (last 20 feet of the lane).
Midline:
A horizontal line that crosses through the center of the grip.
Midplane:
A line perpendicular to the midline that extends through the positive and negative axis points. This line divides the top and bottom halves of the ball on the bowler's axis of rotation.
Oil Patterns:
The way oil is distributed onto the lane.
Particle:
Relates to coverstocks, particle technology consists of small units of various materials added to the shell. Particle coverstocks provide increased traction in the oil.
Pin (on a bowling ball):
The marking on the surface of a bowling ball that indicates the location of the top of the core.
Pin In:
Refers to the weight block being centered in the ball. When this occurs, the pin is within 1" from the CG.
Pin Out:
Refers to the weight block not being centered in the ball. When this occurs, the pin will be more than 1" from the CG.
Pitch:
The angle at which a hole is drilled into a bowling ball.
Plasticizer:
Any of various substances added to plastics or other materials to make or keep them soft or pliable.
Positive Axis Point (PAP):
The point on the opposite side of the track that marks the axis about which the ball is spinning at the point of release.
Preferred Spin Axis (PSA):
The axis through a bowling ball that has the highest radius of gyration.
The distance from the axis of rotation at which one could concentrate the total mass of the bowling ball without changing its rotational properties. The current USBC limits are 2.43 to 2.80.
Revolutions:
The number of times in which the weight block makes one full rotation around the axis line, as it rolls from the foul line to the head pin.
Rev Rate:
A measurement indicating the speed at which the ball is rotating. Usually measured in revolutions per minute.

To calculate a player's total revolutions:
Place a strip of tape from the player's axis point to their ring finger.
Count the revolutions between the player's release and the arrows.
Multiply this number by four (4).

Slower rev rate = stroker - up to 11 revolutions.
Medium rev rate = tweener - from 11 to 17 revolutions.
Faster rev rate = cranker - greater than 17 revolutions.
Skid / Flip:
Refers to a ball reaction that results in excessive backend reaction and increased entry angle.
Span:
The distance between the inside edges of the gripping holes.
Static Weights (top, side and finger):
Fine tubes ball reaction.
Surface:
The composition of the outside of the bowling ball. Also refers to the texture of the coverstock of a bowling ball.
Track:
The surface of the ball that comes into contact with the lane. The track can be found by looking for the oil rings on the ball.
Velocity:
The speed and direction of the bowling ball.
Vertical Axis Line:
A line perpendicular to the midline that crosses through the positive axis point.
Weight Block:
The inner portion of a two piece (or modified two piece) bowling ball which influences ball reaction based on its density and position to the bowlers axis.