Oil of bitter almonds

Almond \Alm"ond\ ([aum]"m[u^]nd), n. [OE. almande, almaunde,
   alemaunde, F. amande, L. amygdala, fr. Gr. 'amygda`lh: cf.
   Sp. almendra. Cf. {Amygdalate}.]
   1. The fruit of the almond tree.
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   Note: The different kinds, as bitter, sweet, thin-shelled,
         thick-shelled almonds, and Jordan almonds, are the
         products of different varieties of the one species,
         {Amygdalus communis}, a native of the Mediterranean
         region and western Asia.
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   2. The tree that bears the fruit; almond tree.
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   3. Anything shaped like an almond. Specifically: (Anat.) One
      of the tonsils.
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   {Almond oil}, fixed oil expressed from sweet or bitter
      almonds.

   {Oil of bitter almonds}, a poisonous volatile oil obtained
      from bitter almonds by maceration and distillation;
      benzoic aldehyde.

   {Imitation oil of bitter almonds}, nitrobenzene.

   {Almond tree} (Bot.), the tree bearing the almond.

   {Almond willow} (Bot.), a willow which has leaves that are of
      a light green on both sides; almond-leaved willow ({Salix
      amygdalina}). --Shenstone.
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Essential \Es*sen"tial\ ([e^]s*s[e^]n"sjal), a. [Cf. F.
   essentiel. See {Essence}.]
   1. Belonging to the essence, or that which makes an object,
      or class of objects, what it is.
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            Majestic as the voice sometimes became, there was
            forever in it an essential character of
            plaintiveness.                        --Hawthorne.
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   2. Hence, really existing; existent.
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            Is it true, that thou art but a name,
            And no essential thing?               --Webster
                                                  (1623).
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   3. Important in the highest degree; indispensable to the
      attainment of an object; indispensably necessary.
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            Judgment's more essential to a general
            Than courage.                         --Denham.
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            How to live? -- that is the essential question for
            us.                                   --H. Spencer.
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   4. Containing the essence or characteristic portion of a
      substance, as of a plant; highly rectified; pure; hence,
      unmixed; as, an essential oil. "Mine own essential
      horror." --Ford.
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   5. (Mus.) Necessary; indispensable; -- said of those tones
      which constitute a chord, in distinction from ornamental
      or passing tones.
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   6. (Med.) Idiopathic; independent of other diseases.
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   {Essential character} (Biol.), the prominent characteristics
      which serve to distinguish one genus, species, etc., from
      another.

   {Essential disease}, {Essential fever} (Med.), one that is
      not dependent on another.

   {Essential oils} (Chem.), a class of volatile oils, extracted
      from plants, fruits, or flowers, having each its
      characteristic odor, and hot burning taste. They are used
      in essences, perfumery, etc., and include many varieties
      of compounds; as {lemon oil} is a terpene, {oil of bitter
      almonds} an aldehyde, {oil of wintergreen} an ethereal
      salt, etc.; -- called also {volatile oils} in distinction
      from the fixed or nonvolatile.
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