This is a noun, but it describes an action. "Characterize" is a verb. The act of characterizing something is "characterization."
1) Is the act of describing the characteristics of something (this is the meaning most commonly used in scientific papers)
"This paper describes the characterization of soil samples collected in the recently reforested Seamus Valley."
Literally, this refers to the act of describing the characteristics, but we usually use it to mean the act of determining those characteristics so that they can be described. It is a very fine distinction and the difference usually moot.
2) Such a description.
"We consulted Lee et al.'s characterization of the protein before analyzing it ourselves."
This refers to the product of the characterization process, the description that Lee and posse produced.
"I disagree with your characterization of Reykjavik as a backward and rustic city. I visited it last year and found it very modern."
3) The establishment or representation of a fictional character.
"Many fans did not like the characterization of Superman in the film Superman Returns, preferring the cheerful, stoic version from the comics."
1) (noun) A trait or quality, especially one that specifically makes it possible to identify something or distinguish it from other things.
"We described the particular characteristics of the ginseng root."
2) (adjective) Relating to a trait that distinguishes a person or thing.
"Recognize the zebra by its characteristic stripes."
"Many photographs of Einstein show his characteristic wild hair."