Mo·tion n.
 1. The act, process, or state of changing place or position; movement; the passing of a body from one place or position to another, whether voluntary or involuntary; -- opposed to rest.
 Speaking or mute, all comeliness and grace
 attends thee, and each word, each motion, forms.   --Milton.
 2. Power of, or capacity for, motion.
    Devoid of sense and motion.   --Milton.
 3. Direction of movement; course; tendency; as, the motion of the planets is from west to east.
    In our proper motion we ascend.   --Milton.
 4. Change in the relative position of the parts of anything; action of a machine with respect to the relative movement of its parts.
    This is the great wheel to which the clock owes its motion.   --Dr. H. More.
 5. Movement of the mind, desires, or passions; mental act, or impulse to any action; internal activity.
    Let a good man obey every good motion rising in his heart, knowing that every such motion proceeds from God.   --South.
 6. A proposal or suggestion looking to action or progress; esp., a formal proposal made in a deliberative assembly; as, a motion to adjourn.
    Yes, I agree, and thank you for your motion.   --Shak.
 7. Law An application made to a court or judge orally in open court.  Its object is to obtain an order or rule directing some act to be done in favor of the applicant.
 8. Mus. Change of pitch in successive sounds, whether in the same part or in groups of parts.
    The independent motions of different parts sounding together constitute counterpoint.   --Grove.
 Note: ☞ Conjunct motion is that by single degrees of the scale. Contrary motion is that when parts move in opposite directions. Disjunct motion is motion by skips. Oblique motion is that when one part is stationary while another moves. Similar or direct motion is that when parts move in the same direction.
 9. A puppet show or puppet. [Obs.]
    What motion's this? the model of Nineveh?   --Beau. & Fl.
 Note: ☞ Motion, in mechanics, may be simple or compound. Simple motions are: (a) straight translation, which, if of indefinite duration, must be reciprocating. (b) Simple rotation, which may be either continuous or reciprocating, and when reciprocating is called oscillating. (c) Helical, which, if of indefinite duration, must be reciprocating. Compound motion consists of combinations of any of the simple motions.
 Center of motion, Harmonic motion, etc. See under Center, Harmonic, etc.
 Motion block Steam Engine, a crosshead.
 Perpetual motion Mech., an incessant motion conceived to be attainable by a machine supplying its own motive forces independently of any action from without.  According to the law of conservation of energy, such perpetual motion is impossible, and no device has yet been built that is capable of perpetual motion.
 Syn: -- See Movement.


 cen·ter n.
 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.
 2. The middle or central portion of anything.
 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 attraction.
 4. The earth. [Obs.]
 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.
 6. Arch. A temporary structure upon which the materials of a vault or arch are supported in position until the work becomes self-supporting.
 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.
 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.
 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.

 ◄ ►