SAVE when you order this item as part of a set. The CDI: Words and Sentences Forms are for use with children ages 16ââ¬"30 months. In the first part of each form, parents document the childâ⬙s production and use of hundreds of words divided into semantic categories. The second part analyzes the early phases of grammar, including the childâ⬙s understanding of word forms and the complexity of the childâ⬙s multi-word utterances. Parents identify the words the child has understood or used and provide written examples of the childâ⬙s three longest sentences. These forms are part of the MacArthur-Bates Communicative Development Inventories (CDIs). The CDIs and their Spanish adaptation, the Inventarios , are standardized, parent-completed report forms that track young children's language and communication skills. Top language researchers developed the report forms, designing them to focus on current behaviors and salient emergent behaviors that parents can recognize and track. This product is sold in a package of 20. Learn more about the MacArthur-Bates CDIs .