Anchor
An anchor is a device, normally made of metal, used to connect a vessel to the bed of a body of water to prevent the craft from drifting due to wind or current. The word derives from Latin "ancora", which itself comes from the Greek ἄγκυρα ("ankura").
Anchor
The vessel is attached to the anchor by the "rode" (commonly called "cable" when made of rope, and made of chain in larger vessels), or a combination of these. The ratio of the length of rode to the water depth is known as the scope; generally, the rode should be between 5 and 10 times the depth of the seabed, giving a scope of 5:1 or 10:1; the larger the number, the shallower the angle is between the cable and the seafloor, and the less upwards force is acting on the anchor. A 10:1 scope gives the greatest holding power, but also allows for much more drifting due to the longer amount of cable paid out. Anchoring with sufficient scope and/or heavy chain rode brings the direction of strain close to parallel with the seabed. This is particularly important for light, modern anchors designed to bury in the bottom, where scopes of 5- to 7-to-1 are common, whereas heavy anchors and moorings can use a scope of 3-to-1, or less.