subitize

• subitise (British)

From Latin subitus (“sudden; unexpected”) +‎ -ize, from the feeling of immediately knowing the number of items present. Doublet of sudden.

subitize (third-person singular simple present subitizes, present participle subitizing, simple past and past participle subitized)

1. (transitive, intransitive, psychology) To judge (the number of objects in a group) rapidly, accurately and confidently without counting them. [from 1949]
   • 2002, Kelly S. Mix, Janellen Huttenlocher, Susan Cohen Levine, Quantitative Development in Infancy and Early Childhood, Oxford University Press (→ISBN), page 47:

     Previous researchers have noted a similarity between the set sizes that adults can estimate rapidly, or subitize, and the set sizes that infants can discriminate: both are less than five items. This similarity has led some to suggest that subitizing is […]

   • 2016, Jennifer Taylor-Cox, Math Intervention P–2: Building Number Power with Formative Assessments, Differentiation, and Games, Grades PreK–2, Routledge (→ISBN), page 52:

     When students subitize, they know how many because the arrangement is familiar and/or friendly. While recent information about the benefits of teaching subitizing has surfaced (Clements, 1999), early use of the term appeared more than […]

• subitive

• French numéron