Pronunciation - Pronunciation, stress, rhythm, and intonation, though possibly influenced by the first language or regional variation, almost never interfere with ease of understanding.

Structure - Both basic and complex grammatical structures and sentence patterns are consistently well controlled.

Vocabulary - Vocabulary range and accuracy are sufficient to communicate  effectively on a wide variety of familiar and unfamiliar topics.  Vocabulary is idiomatic, nuanced, and sensitive to register.

Comprehension - Comprehension is consistently accurate in nearly all contexts and includes comprehension of linguistic and cultural subtleties.

Fluency - Able to speak at length with a natural, effortless flow.  Varies speech flow for stylistic effect, e.g. to emphasize a point.  Uses appropriate discourse markers and connectors spontaneously.

Interaction - Interacts with ease in nearly all situations.  Is sensitive to verbal and non-verbal cues and responds to them appropriately.