neutral surface

Neutral \Neu"tral\, a. [L. neutralis, fr. neuter. See {Neuter}.]
   1. Not engaged on either side; not taking part with or
      assisting either of two or more contending parties;
      neuter; indifferent.
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            The heart can not possibly remain neutral, but
            constantly takes part one way or the other.
                                                  --Shaftesbury.
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   2. Neither good nor bad; of medium quality; middling; not
      decided or pronounced.
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            Some things good, and some things ill, do seem,
            And neutral some, in her fantastic eye. --Sir J.
                                                  Davies.
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   3. (Biol.) Neuter. See {Neuter}, a., 3.
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   4. (Chem.) Having neither acid nor basic properties; unable
      to turn red litmus blue or blue litmus red; -- said of
      certain salts or other compounds. Contrasted with {acid},
      and {alkaline}.
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   {Neutral axis}, {Neutral surface} (Mech.), that line or
      plane, in a beam under transverse pressure, at which the
      fibers are neither stretched nor compressed, or where the
      longitudinal stress is zero. See {Axis}.

   {Neutral equilibrium} (Mech.), the kind of equilibrium of a
      body so placed that when moved slighty it neither tends to
      return to its former position not depart more widely from
      it, as a perfect sphere or cylinder on a horizontal plane.
      

   {Neutral salt} (Chem.), a salt formed by the complete
      replacement of the hydrogen in an acid or base; in the
      former case by a positive or basic, in the latter by a
      negative or acid, element or radical.

   {Neutral tint}, a bluish gray pigment, used in water colors,
      made by mixing indigo or other blue some warm color. the
      shades vary greatly.

   {Neutral vowel}, the vowel element having an obscure and
      indefinite quality, such as is commonly taken by the vowel
      in many unaccented syllables. It is regarded by some as
      identical with the [u^] in up, and is called also the
      {natural vowel}, as unformed by art and effort; it is also
      called the {indefinite vowel}. It is symbolized in some
      phonetic alphabets by the {schwa} ([schwa]). See Guide to
      Pronunciation, [sect] 17.
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