impetus

The word "impetus" refers to the force or motivation that starts something happening, or causes it to grow and develop. It's more than just a simple push; it's the driving power behind change, progress, or movement. The word comes from Latin, originally meaning "attack" or "assault," hinting at its forceful nature.

You might say a personal tragedy provided the impetus for an artist to create their most powerful work. Or that economic hardship gave impetus to social reform. It's often used when discussing significant shifts or developments – things don't just happen, they are usually driven by some kind of impetus.

Impetus can be tangible, like a financial incentive, or intangible, like a surge of inspiration. A new law might provide the impetus for businesses to adopt more sustainable practices. The desire for social justice is often a strong impetus behind protest movements. It can come from outside, like a new policy or a sudden event, or from within, like a strong wish to change something.

So, when you see or hear about something gaining momentum, look for the impetus—the driving force that's making it all happen. It's the "why" behind the movement, the spark behind the change.