Negative:  1.) Any image with tones that are the reverse of those in the subject.  Opposite:  positive.  2.)  The film is the camera during exposure that is subsequently developed to produce a negative image.

Negative carrier:  A frame that holds a negative flat in an enlarger.

Negative film:  Film that produces a negative image on exposure and development.

Non-silver process:  A film process that does not depend on the sensitivity of silver to form an image; for example, the cyanotype process, in which the light sensitive emulsion consists of a mixture of iron salts.

Normal lens:  A lens whose focal length is about the same as the diagonal measurement of the film with which it is used.  The angle of view with this lens-film size combination is roughly the same at a given distance as the angle that the human eye sees clearly.

Notching code:  Notches cut in the margin of sheet film so that the type of film and its emulsion side can be identified in the dark.