Two-year-old Bella is undergoing a "vocabulary explosion," learning as many as 50 new words a day. In most instances, Bella is probably learning to identify concepts.

Mid-level concepts

Explanation:

Two years Bella is going under the concept of mid-level. She has been exposed to her vocabulary daily around 50 words. Because she has been identified the concepts of the mid-level.

This time she is learning more and more about the new words. This is her age when she excited to know about new things about life. She learns through the environment and family members. She will learn from family members and friends.

what terms are there?

sounds good to me mate!