What is the term for the language stage where whole ideas are expressed in one word, usually between ages 1 and 2?

The term for the language stage where whole ideas are expressed in one word, typically occurring between ages 1 and 2, is indeed referred to as the one-word stage. During this stage, children often use single words to convey a complete thought or idea, such as "milk" to express a desire for milk or "up" to indicate they want to be picked up. This stage is crucial in language development as it marks the transition from nonverbal to verbal communication, allowing children to begin to express their needs, wants, and observations using language.

The one-word stage is significant because it illustrates how infants start to understand that words represent objects, actions, or feelings. As they progress, they often expand their vocabulary and begin to combine words to form more complex expressions.