a stage in language development, usually occurring during a child’s 2nd year, when a marked increase occurs in the rate at which new words are added to the child’s productive vocabulary. This stage marks a change in the cognitive and linguistic underpinnings of children’s language use: It indicates their increased understanding that words are symbols that refer to actual things in the world, and it is thought to explain why nouns in particular are acquired at a rapid rate. Also called vocabulary spurt; word spurt.