OS X Yosemite was a visual watershed moment for Apple, but 10.10.5 is the specific "final patch" version that made it stable. If you are running a Mac from 2009–2013, Yosemite 10.10.5 is often the sweet spot for features vs. performance. However, on newer machines, it is obsolete, and on older machines, it can feel sluggish compared to OS X Mavericks (10.9).
If you previously "purchased" Yosemite, it might still appear in your Purchased tab. mac os x yosemite 10.10 5 download dmg
(approx. 2.12 GB) allows you to update from any previous 10.10 version directly. Alternate Source : Some users utilize repositories like the macOS-ISOs GitHub for historical disk images. Apple Support Informative Review Key Features & Strengths Mac OS X 10.10 Yosemite Review! OS X Yosemite was a visual watershed moment