Present participle of alphabetize; the ongoing action of arranging things in alphabetical order.
Alphabetize + -ing (the present participle suffix). The -ing suffix comes from Old English -ing and -ung and creates the continuous or progressive form of verbs.
The -ing form of verbs is incredibly flexible in English—it can be a verb (is alphabetizing), a noun (alphabetizing is boring), or an adjective (an alphabetizing system)—giving speakers three uses from one ending.
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