English, squirt, swerve and throw.

What english is for

English is side spin, put on the cue ball by striking it left or right of center. Its main job is to change the cue ball's path after it bounces off a cushion, not its path to the object ball. Left spin makes the cue ball rebound to the left off a cushion; right spin, to the right. Players name it by use: inside, outside, running or reverse english.

Dr. Dave Alciatore's advice is not to use side spin unless you need it; unneeded side spin is on his list of the ten things players most often do wrong. On straight-in shots, he suggests "cheating the pocket" instead: aiming the object ball slightly off the pocket's center to change the cue ball's angle without spin.

Squirt: the cue ball pushes off line

When you hit the cue ball off center, it does not leave exactly along the line of your cue; it leaves at a slight angle to it. That is squirt (also called deflection), and it grows with the amount of side spin. Squirt does not depend on shot speed. It depends on the mass at the end of the shaft, which is why low-squirt shafts are built with less mass near the tip. Dr. Dave names Predator, OB-1 and Universal SmartShaft as examples, and notes that switching to one means relearning your aim compensation.

Swerve: the cue ball curves

A spinning cue ball that is still sliding curves on the cloth. Swerve increases with cue elevation and with side spin, shows up later on faster shots, and only happens while the ball is sliding. Keeping the cue level helps limit it.

Squerve: the combined effect

The net result of squirt plus swerve is called squerve. For a given distance, spin and cue, there is a combination of speed and elevation at which squerve is zero.

Compensating: back-hand and front-hand english

• Back-hand english (BHE). Aim for a center-ball hit, then pivot the cue with your grip hand, keeping the bridge fixed, until the tip reaches the side-spin position you want. If your bridge is at the cue's "natural pivot length," this cancels squirt.
• Front-hand english (FHE). Pivot at the bridge hand instead. It suits low-squirt cues, which need less pivot.

Figures quoted on Dr. Dave's site put the natural pivot length at roughly 9 to 9.5 inches for a normal shaft and about 12 to 14 inches for low-squirt shafts. On most side-spin shots swerve is significant too, so back-hand english alone does not fully compensate; his SAWS method combines both pivots.

Throw: the object ball goes off line

Throw is the object ball leaving slightly off the line through the two balls' centers, caused by friction between them at contact. It has two sources: the cut angle (cut-induced throw) and side spin (spin-induced throw).

• How much. Maximum throw is generally about 1 inch per foot of object ball travel, about 5 degrees, roughly half a ball per diamond on a 9-foot table.
• What reduces it. Topspin or backspin at contact cuts throw by up to about 75 percent at cut angles up to about 30 degrees.
• When it peaks. Spin-induced throw is greatest on a slow, straight stun shot with about half of maximum side spin.
• Gearing outside english. Just the right amount of outside english produces no throw at all; the amount needed rises with the cut angle, to about half of maximum at a half-ball hit. Too much throws the object ball the other way.
• Inside english produces more consistent throw across tip positions than outside english, and fast inside-english shots throw the least.

One more source of throw is dirt. Chalk marks on the balls can cause "cling," "skid" or "kick," an extra-large throw. Wipe the cue ball clean whenever you get the chance, such as before the break or when you have ball in hand.