An impetus is the force or motivation that makes something begin or continue. When your teacher announces a pizza party for the class that reads the most books, that announcement provides the impetus for everyone to start reading more. The promise of pizza gets things moving.

A rolling ball has impetus that keeps it rolling until friction stops it. We mostly use the word today for the push that starts projects, movements, or changes.

Sometimes impetus comes from inside you: curiosity might provide the impetus for learning to code. Other times it comes from outside: a new school policy might provide the impetus for students to organize a petition. Major historical events often serve as the impetus for important changes. The launch of Sputnik by the Soviet Union in 1957 provided the impetus for America to dramatically expand its space program and math education.

When something lacks impetus, it stalls out. When something gains impetus, it picks up speed and momentum. The word captures that crucial spark or push that transforms “maybe someday” into “let's do this now.”