many+kinds

  • 131Acoustics — is the interdisciplinary science that deals with the study of sound, ultrasound and infrasound (all mechanical waves in gases, liquids, and solids). A scientist who works in the field of acoustics is an acoustician. The application of acoustics… …

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  • 132Screw — This article is about the fastener. For other uses, see Screw (disambiguation). Screws come in a variety of shapes and sizes for different purposes. U.S. quarter coin (diameter 24 mm) shown for scale. A screw, or bolt, is a type of fastener… …

    Wikipedia