chemical: A substance formed from two or more atoms that unite (bond) in a fixed proportion and structure. For example, water is a chemical made when two hydrogen atoms bond to one oxygen atom. Its chemical formula is H2O. Chemical also can be an adjective to describe properties of materials that are the result of various reactions between different compounds.
millisecond: A thousandth of a second.
perception: The state of being aware of something — or the process of becoming aware of something — through use of the senses.
pressure: Force applied uniformly over a surface, measured as force per unit of area.
psychology: (adj. psychological ) The study of the human mind, especially in relation to actions and behavior. To do this, some perform research using animals. Scientists and mental-health professionals who work in this field are known as psychologists.
sequence: The precise order of related things within some series.
trillion: A number representing a million million — or 1,000,000,000,000 — of something.