Limb

limb¹

1. an arm or leg, or the analogous part on an animal, such as a wing

2. any of the main branches of a tree

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limb²

1. the edge of the apparent disc of the sun, a moon, or a planet

2. Botany

a. the expanded upper part of a bell-shaped corolla

b. the expanded part of a leaf, petal, or sepal

3. either of the two halves of a bow

4. either of the sides of a geological fold

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limb [limb]

(anatomy)

An extremity or appendage used for locomotion or prehension, such as an arm or a leg.

(astronomy)

The circular outer edge of a celestial body; the half with the greater altitude is called the upper limb, and the half with the lesser altitude, the lower limb.

(botany)

A large primary tree branch.

(design engineering)

The graduated margin of an arc or circle in an instrument for measuring angles, as that part of a marine sextant carrying the altitude scale.

The graduated staff of a leveling rod.

(geology)

One of the two sections of an anticline or syncline on either side of the axis. Also known as flank.

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Limb 

a flat metal ring divided by lines into equal parts of circumference (for example, degrees or minutes). It is the most important part of instruments used in measuring angles (in astronomy, geodesy, physics, and so on); it gives a reading of the magnitude of the angle. The scale units of a limb are read by means of a vernier or a micrometric microscope.