Semantic roles.
Agent and theme.
agent. one role is taken by the noun phrase The boy as “the entity
that performs the action,”
theme. Another role is taken by the
ball as “the entity that is involved in or affected by the action,”
Agents and themes are the most common semantic roles.
Although agents are
typically human (The boy), they can also be non-human entities
that cause actions,
as in noun phrases denoting a natural force (The wind),