1. The apparent surface of the imaginary sphere on which celestial bodies appear to be projected
   - celestial sphere, sphere, empyrean, firmament, heavens, welkin

Type of: surface

• achromatous
• achromia
• achromic
• achromous
• Achromycin
• achy
• achylia
• achylia gastrica
• acicula
• acicular
• aciculate
• acid
• acid anhydrides
• acid dye
• acid halide
• acid head
• acid hydrogen
• acid precipitation
• acid rain
• acid rock
• acid test
• acid value
• acid-base balance
• acid-base equilibrium
• acid-base indicator