For one thing Definition 1 of 1Pro Tip 1/3Starting List Use it to start listing reasons, with more points to follow. I prefer biking – for one thing, it's great exercise. Pro Tip 2/3Emphasis on Importance Highlight a prominent reason or factor in an argument or decision. This plan is flawed – for one thing, the costs are underestimated. Pro Tip 3/3Introduce Specifics Shift from general discussion to specific examples or details. Our city needs improvements – for one thing, the public transport system is outdated.