Holophrastic Stage: This is an earlier stage in language development where children use single words to express complete thoughts. For example, saying "juice" when they want some juice.
Overextension: This is when children apply rules of grammar too broadly and incorrectly. For instance, adding 'ed' to all past tense verbs even if it's not grammatically correct (e.g., "I goed home").
Morpheme: The smallest meaningful unit of language. It can be as short as one letter or as long as several letters.