After the appearance of their first words, children typically develop their vocabulary slowly until they have a "spurt" at around 18 months, when they reach an average level of productive vocabulary words.

50

Explanation:

Productive vocabulary words refers to Vocabulary of an person as defined by the words he or she utilizes on a constant basis, as compared for those he or she may recognize when used by others. Productive knowledge of vocabulary is the capacity to use various aspects of word knowledge in writing and speech.

Children typically slowly continuously grow there productive vocabulary words and experiences a sprunt At around 18 months when they reach their 50 productive vocabulary words