center \cen"ter\ (s[e^]n"t[~e]r), n. [F. centre, fr. L. centrum,
fr. Gr. ke`ntron any sharp point, the point round which a
circle is described, fr. kentei^n to prick, goad.]
1. A point equally distant from the extremities of a line,
figure, or body, or from all parts of the circumference of
a circle; the middle point or place.
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2. The middle or central portion of anything.
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3. A principal or important point of concentration; the
nucleus around which things are gathered or to which they
tend; an object of attention, action, or force; as, a
center of attaction.
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4. The earth. [Obs.] --Shak.
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5. Those members of a legislative assembly (as in France) who
support the existing government. They sit in the middle of
the legislative chamber, opposite the presiding officer,
between the conservatives or monarchists, who sit on the
right of the speaker, and the radicals or advanced
republicans who occupy the seats on his left, See Right,
and Left.
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6. (Arch.) A temporary structure upon which the materials of
a vault or arch are supported in position until the work
becomes self-supporting.
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7. (Mech.)
(a) One of the two conical steel pins, in a lathe, etc.,
upon which the work is held, and about which it
revolves.
(b) A conical recess, or indentation, in the end of a
shaft or other work, to receive the point of a center,
on which the work can turn, as in a lathe.
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Note: In a lathe the
live center is in the spindle of the head stock; the
dead center is on the tail stock.
Planer centers are stocks carrying centers, when the object
to be planed must be turned on its axis.
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Center of an army, the body or troops occupying the place
in the line between the wings.
Center of a curve or Center of a surface (Geom.)
(a) A point such that every line drawn through the point
and terminated by the curve or surface is bisected at
the point.
(b) The fixed point of reference in polar coordinates. See
Coordinates.
Center of curvature of a curve (Geom.), the center of that
circle which has at any given point of the curve closer
contact with the curve than has any other circle whatever.
See Circle.
Center of a fleet, the division or column between the van
and rear, or between the weather division and the lee.
Center of gravity (Mech.), that point of a body about which
all its parts can be balanced, or which being supported,
the whole body will remain at rest, though acted upon by
gravity.
Center of gyration (Mech.), that point in a rotating body
at which the whole mass might be concentrated
(theoretically) without altering the resistance of the
intertia of the body to angular acceleration or
retardation.
Center of inertia (Mech.), the center of gravity of a body
or system of bodies.
Center of motion, the point which remains at rest, while
all the other parts of a body move round it.
Center of oscillation, the point at which, if the whole
matter of a suspended body were collected, the time of
oscillation would be the same as it is in the actual form
and state of the body.
Center of percussion, that point in a body moving about a
fixed axis at which it may strike an obstacle without
communicating a shock to the axis.
Center of pressure (Hydros.), that point in a surface
pressed by a fluid, at which, if a force equal to the
whole pressure and in the same line be applied in a
contrary direction, it will balance or counteract the
whole pressure of the fluid.
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