Final answer:
The Emergent stage is when a learner uses individual words without forming complete sentences, rapidly expanding their vocabulary.
Step-by-step explanation:
The stage in which a learner starts using some words but has not yet mastered forming sentences is known as the Emergent stage. During this phase, a child typically uses single words to express a variety of ideas, relations, and desires. This is a crucial stage in language development where children begin to expand their vocabulary rapidly, learning new words every week, but are not yet fluent in sentence construction.