BeamBauThe maximum width of a boat's hull, measured at its widest point. Beam directly shapes interior volume, form stability and marina fees: a wider hull resists heeling and houses larger cabins, but adds drag and weight. Comparing two yachts of equal length, the beamier one almost always feels bigger below deck — and costs more to berth.CE categoryCatégorie CEA European design classification stating the conditions a recreational craft is built to handle: A (ocean), B (offshore), C (inshore) and D (sheltered waters), each defined by maximum wind force and significant wave height. It rates the boat, not the crew. When buying, check the category matches your intended cruising ground — and remember it assumes sound maintenance and reasonable loading.CockpitCockpitThe open, usually recessed area of the deck from which the crew steers and works the boat. On sailing yachts it concentrates helm, winches and lines; on motor yachts it usually refers to the aft-deck living space. Depth, drainage, handholds and protection from spray decide how safe and comfortable a boat feels underway — inspect it as carefully as the saloon.DisplacementDéplacementThe weight of water a hull pushes aside when afloat — in practice, the boat's actual weight, usually quoted in tonnes. Light displacement means the empty boat; loaded displacement includes fuel, water and gear. It drives motion comfort, load-carrying ability and fuel consumption: heavier hulls ride softer through chop but need more power, lighter ones accelerate and sip fuel.DraftTirant d'eauThe vertical distance between the waterline and the deepest point of the boat, usually the keel or the propellers. Draft dictates where you can go: shallow anchorages, rivers and tidal harbours all set hard limits. Sailing yachts trade draft against stability — deep keels stiffen the boat — while catamarans and lifting-keel designs buy access to water others must avoid.Flag statePavillonThe country where a vessel is registered and whose laws govern it at sea. The flag determines taxation, safety rules, crew requirements and, for charter, what commercial use is allowed. Owners choose between home registration and popular registries such as Malta, the Cayman Islands or Belgium for fiscal or regulatory reasons — a decision best made with specialist advice before purchase, not after.FlybridgeFlybridgeAn open upper deck above the main wheelhouse, fitted with a second helm station and usually sunpads, seating and a wet bar. It offers excellent visibility for manoeuvring and doubles the outdoor living area. The trade-offs: extra height and windage, more weight up high, and a boat that may no longer pass under certain bridges or fit standard storage sheds.Hard-topHard-topA rigid roof — usually fibreglass or carbon — covering the helm or cockpit area, often incorporating an opening section. Compared with a canvas bimini, it shrugs off sun, rain and years of UV without sagging, and it carries lights, antennas and solar panels. It adds weight, height and cost, but on a boat used year-round it generally earns all three.Hull formCarèneThe underwater shape of the hull, which governs how a boat moves through water. Planing hulls climb over their bow wave and run fast; displacement hulls push through it, efficient but speed-limited; semi-displacement forms sit in between. Chines, deadrise angle and rocker each tune the compromise between speed, comfort, stability and fuel burn — no single shape wins everywhere.KnotNœudThe unit of speed at sea: one nautical mile (1,852 metres) per hour. The name survives from the knotted log line sailors once paid out to time a ship's way. A displacement yacht typically cruises at 7–9 knots, a planing motor yacht at 20–30. Multiply knots by 1.85 for km/h — useful when turning range figures into passage plans.Length overall (LOA)Longueur hors tout (LHT)The full length of a boat from the tip of the bow — fixed bowsprit or anchor gear included — to the aftmost point of the stern, swim platform included. LOA is the figure marinas, insurers and regulations rely on, so it drives most recurring costs. Compare it with hull length: builders sometimes market one and invoice the other.OsmosisOsmoseA slow degradation of fibreglass hulls in which water migrates through the gelcoat and reacts with the laminate, forming acidic blisters below the waterline. It is rarely structural if caught early, but treatment — peeling, drying, epoxy barrier — is long and expensive. On any used boat, a moisture-meter survey of the hull is the cheapest insurance you will ever buy.RigGréementThe system of masts, spars, standing rigging (the wires holding the mast up) and running rigging (the lines that hoist and trim sails). The sloop — one mast, mainsail and headsail — dominates modern cruising for its simplicity. Standing rigging has a finite life, typically 10–15 years or one circumnavigation: budget for its replacement when buying an older sailing yacht.Semi-displacementSemi-déplacementA hull form that bridges displacement and planing designs: given enough power it partially lifts and exceeds classic hull speed without fully climbing onto the plane. Typical of trawlers and Downeast-style motor yachts, it delivers a comfortable 12–18-knot cruise, decent seakeeping and moderate fuel burn — a sensible middle path for owners who value range over outright speed.