The phrase "discernible change" means a noticeable or visible difference. It refers to something that can be perceived, observed, or understood easily. Full definition
Teachers select recommendations developed by our policy teams to design campaign strategies to move our recommendations into discernible changes in policy and practice. (teachersunitedwa.org)
Mutations give rise to new genes, but only some of those produce discernible changes that improve (or reduce) fitness. (discovermagazine.com)
If anything, our projections for warming are higher than they used to be, and we're seeing discernible changes in ecosystems that we can link back to climate.» (nytimes.com)