Normal

Part of speech: noun (n.)

A straight line or plane drawn from any point of a curve or surface so as to be perpendicular to the curve or surface at that point.

Part of speech: adjective (a.)

1. According to an established norm, rule, or principle; conformed to a type, standard, or regular form; performing the proper functions; not abnormal; regular; natural; analogical. Deviations from the normal type. Hallam.

2. According to a square or rule; perpendicular; forming a right angle. Specifically: Of or pertaining to a normal.

3. Standard; original; exact; typical. Specifically:

4. Denoting certain hypothetical compounds, as acids from which the real acids are obtained by dehydration; thus, normal sulphuric acid and normal nitric acid are respectively S(OH)6, and N(OH)5.

Synonyms: Normal, Regular, Ordinary. Regular and ordinary are popular terms of well-known signification; normal has now a more specific sense, arising out of its use in science. A thing is normal, or in its normal state, when strictly conformed to those principles of its constitution which mark its species or to the standard of a healthy and natural condition. It is abnormal when it departs from those principles.