Center of Gravity - or "CG," is the point in the clubhead where all lines of balance intersect, and where the entire mass is at equilibrium in all directions.

Where the CG is positioned can affect launch angle. Generally, the higher the CG (farther from the ground), the lower the launch angle. By strategically distributing the weight in the clubhead, club designers can position the CG lower and farther back in the clubhead to produce a higher launch angle, which generally results in more carry and greater distance.

Coefficient of Restitution, or "COR" - relates to the energy transfer that occurs when one object collides with another. In terms of golf clubs, COR is directly related to the speed of a golf ball as it rebounds from a clubface. Generally, a club with higher COR will generate greater ball velocity, equaling more distance.

COR is expressed as a percentage. To measure a club's COR, balls are fired at a clubface at a fixed speed, known as initial speed. The speed at which the balls rebound is known as rebound speed. The COR is generally equal to the rebound speed divided by the initial speed. For example, if the initial speed is 100 mph, and the rebound speed is 84 mph, the COR would be approximately .840.

The Rules of Golf maintained by the USGA limits the COR on driving clubs to .830.

In terms of distance, a player with a swing speed from 100 to 120 mph should gain about two yards for every one percent increase in COR. Players with slower swing speeds will generally gain less yardage.

Moment of Inertia - is the measure of an object's ability to resist angular momentum. In terms of golf clubs, a club's moment of inertia refers to its force at impact and to its ability to resist twisting on off-center hits.

A one-pound weight swinging on a one-foot rope has an MOI of one-pound-feet2. The MOI of this one-pound weight will increase if the length of the rope is increased; specifically, MOI multiplies by the square of the distance of its radius. Thus, a one-pound weight swinging from a three-foot rope has an MOI of nine-pound-feet2.

In a clubhead, MOI is generally measured by squaring the distance of the radius as measured from the CG to the club's outside edges. Consequently, oversize clubheads have a greater MOI than smaller clubheads.

The ability of a clubhead to resist twisting on off-center hits is crucial, especially to recreational golfers, who frequently make contact away from the center of the clubface. A club with low MOI will tend to twist open when contact is made toward the toe and closed when contact is made toward the heel, and the direction of the shot suffers and COR drops. Although a higher MOI will not remedy loss of COR on off-center hits, it will make the head more resistant to twisting, resulting in a straighter shot.

Spring-Like Effect - is a term sometimes used to describe the way a thin metalwood clubface behaves at impact by flexing and rebounding. In general, the more the clubface flexes at impact, the higher the club's COR will be.

Spin Rate - A golf ball's spin rate refers to the speed it spins on an axis while in flight, measured in revolutions per minute (rpm). Spin rate off a driver generally ranges between 2,000 and 4,000 rpm, while the average, cleanly struck wedge shot spins at about 10,000 rpm. Spin generates lift, thus a shot's spin rate directly influences how high the ball flies and how quickly it stops after landing.

Swing Weight - Whereas a club's total weight refers to how much it weighs when placed on a scale, a club's swing weight refers to how light or heavy it feels to swing. Swing weight is determined by the ratio of weight concentrated in both ends of the club. The clubhead-end is always heavier than the grip end; however, the larger the discrepancy in weight between the head-end and grip-end, the heavier the club will feel to swing, and the heavier its swing weight will be. Swing weight is identified using a letter combined with a number, e.g. C-3 and D-1; the higher each one is, the heavier the swing weight . For example, a club measuring C-5 has a heavier swing weight than a C-4; and a club measuring D-1 is heavier than a C-5. Drivers are usually balanced around D-2 for men while wedges are usually heavier, around D-5. Drivers for women are usually around C-5.