"Twenty Fifteen is the default theme for WordPress in 2015. It is super-clean, content-focused, and designed to bring a little more simplicity to our blogs. Its careful attention to typography, featuring the expertly-designed Noto font set in elegant and harmonious margins, makes it beautiful in multiple languages around the world."
Twenty Fifteen's simple, straightforward typography is readable on a wide variety of screen sizes, and suitable for multiple languages. We designed it using a mobile-first approach, meaning your content takes center-stage, regardless of whether your visitors arrive by smartphone, tablet, laptop, or desktop computer.
(NOTE: this is at WordPress.org where you can edit the backend – so some of the solutions do not apply if you are using it at wordpress.com)