tail assembly: see airplane.

mare's-tail, any plant of the genus Hippuris, perennial, submerged aquatic herbs of temperate and frigid regions. Mare's-tails have an erect stem bearing whorls of small leaves, so they resemble some of the horsetails (which are also sometimes called mare's-tails); however, unlike horsetails, they are flowering plants, with the inconspicuous flowers borne in the leaf axils. Mare's-tails are cultivated in bog gardens. They are classified in the division Magnoliophyta, class Magnoliopsida, order Callitrichales, family Hippuridaceae.

Extension of the vertebral column beyond the trunk, or any slender projection resembling such a structure. In fishes and other animals living completely or partly in water, it is very important to movement through water. Many tree-dwelling animals (e.g., squirrels) use the tail for balance and as a rudder when leaping; in some (e.g., certain monkeys), it is adapted for grasping. Birds' tail feathers aid in flight maneuverability. Other animals use their tails for defense (e.g., porcupines), social signals (e.g., dogs and cats), warning signals (e.g., deer and rattlesnakes), and hunting (e.g., alligators).

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