1914 introductions

mask protecting from toxic molecules and particles

Hornbostel–Sachs or Sachs–Hornbostel is a system of musical instrument classification devised by Erich Moritz von Hornbostel and Curt Sachs. This system was first published in the in 1914. An English translation was published in the Galpin Society Journal in 1961, which is the most widely used system for classifying musical instruments by ethnomusicologists and organologists (people who study musical instruments). The system was updated in 2011 as part of the work of the Musical Instrument Museums Online (MIMO) Project.

cone-shaped marker used for traffic management

In mathematics, the hyperoperation sequence is an infinite sequence of arithmetic operations (called hyperoperations in this context) that starts with a unary operation (the successor function with n = 0). The sequence continues with the binary operations of addition (n = 1), multiplication (n = 2), and exponentiation (n = 3). After that, the sequence proceeds with further binary operations extending beyond exponentiation, using right-associativity. For the operations beyond exponentiation, the nth member of this sequence is named by Reuben Goodstein after the Greek prefix of n suffixed with -

thumb|Painting with acrylic paint on the reverse side of an already inked cel.

1915 class of German small coastal submarines

British military rank