Graphology - the study of handwritings; autograph - written with one's own hand; seismograph - a machine noting strength and duration of earthquakes. marina - a harbor for pleasure boats; maritime - relating to the sea; submarine - an undersea boat; aquamarine - color of sea water.
Chemicals are classified into various hazard classifications in accordance with their physiochemical properties and health hazards. Each class of chemical has a pictorial symbol called a danger symbol.
Class 6: Toxic and infectious substances: Class 6 DOT placards indicate if a substance is toxic or infectious. The former category is largely self-explanatory; the latter is used primarily on biohazard waste, which the World Health Organization subdivides into the categories of infectious and samples.