Which noun identifies a group acting as one?

The term that identifies a group acting as one is "collective." This noun specifically refers to a collection of individuals or items that are considered as a single entity or unit. For instance, in language, a collective noun can describe groups such as "team," "flock," or "committee," where the focus is on the group functioning together rather than on individual members.

In contrast, the other types of nouns do not convey the same meaning. Proper nouns are names of specific people, places, or organizations, and they refer to unique entities rather than groups acting in unison. Common nouns are general names for a person, place, or thing and do not indicate a collective nature. Abstract nouns represent concepts or ideas rather than tangible entities and typically do not describe a group acting as one. Therefore, "collective" is the most suitable choice for identifying a group that operates in unity.