* The new CEO's arrival acted as a catalyst for positive change in the company. (This sentence implies that the CEO's arrival was the reason for change happening.)
* The recent economic downturn served as a catalyst for people to re-evaluate their spending habits. (This sentence indicates that the economic downturn made people think differently about their finances.)
* The discovery of penicillin was a catalyst for the development of antibiotics. (This sentence explains that penicillin was a key factor in the creation of antibiotics.)
* Her passionate speech was the catalyst that ignited the protest movement. (This sentence shows that her speech was the reason the protest started.)
* The unexpected rain acted as a catalyst for the growth of the wildflowers. (This sentence uses "catalyst" in a more literal sense, showing that the rain directly helped the flowers grow.)
These sentences demonstrate how "catalyst" can be used to describe a person, event, or even a natural phenomenon that triggers or accelerates a change or reaction.