Running Rigging Glossary

Sailboat Rigging can be divided in to 2 categories:

Standing Rigging - the wires and ropes that hold up the mast, also known as shrouds or stays

Running Rigging - the ropes (and wires) that control the sails on a yacht.

There are a large number of different terms that cover the use for which each rope is employed.

The most common generic terms are sheets and halyards.

Sheets

Normally attached to the clew of the sail and control the shape and angle to the wind - each individual sheet is identified by the name of the sail as a prefix e.g. Jib sheets, genoa sheets, yankee sheets, staysail sheets, code zero sheets, gennaker sheets, cruising chute sheets, mainsheets, mizzen sheets - where these are a pair, they may also be classified as port or starboard. Spinnaker Sheets are used in conjunction with Spinnaker Guys and a spinnaker pole to control the shape of the spinnaker on either gybe

Halyards

Attached to the head of a sail and used to haul a sail up the mast - in the same way as sheets, each halyard is identified by the name of the sail as a prefix e.g. main halyard.

Sheets and halyards are part of a more generic category: Control Lines or a little more obscurely, Preventers
Control Lines include sheets and halyards and all the other ropes and wires that contribute to the efficient mangement of a yacht's sail area.
A rope that stops an accidental gybe is commonly referred to as a preventer.
However, most of the ropes that comprise a yacht's running rigging can be described as preventers i.e. a rope that is preventing something or control lines i.e. a rope that is controlling something

Control Lines:

Tack Line 
- attached to the tack of a sail to make the length of the luff adjustable - common on loose footed reaching/running headsails e.g. gennakers but also used on more traditional rigs e.g. dipping lugsails

In Hauler or Tweaker - attached to a headsail (jib/genoa/yankee/code zero) sheet and used to bring the angle of the lead nearer to the centreline than the normal setting.

Barber Hauler - attached to a headsail sheet and used to create more downward pressure and generally from a point further outboard than the normal fairlead setting

Downhaul or Cunningham - attached to the tack of a mainsail and used to create tension in the luff.

Kicker or Vang - diagonal line or purchase system (block and tackle) from base of mast to a point on the underside of the boom - used to create downward tension on the boom and subsequently the leach of the sail

Outhaul - generally attached to the clew of a mainsail to adjust the foot tension

Reefing Line or Reefing Pennant - Lines reeved through the boom and the mainsail to facilitate a reduction in mainsail area

Lazyjack Line - used for guiding and controlling the mainsail as it is dropped

Running Backstays or Checkstays - adjustable version of the backstay, generally consisting of a very low stretch standing part (single line) attached to a purchase system for adjusting the tension

Preventer - line deployed to prevent the mainsail boom from accidentally gybing or control the speed of the boom's transition during a gybe