Calm
Mild
noun, な adjective
This is a な adjective version of the kanji which means calm. The vocab version here is calm as well, though you can use it to mean mild as well.
What is calm? "Ode (おだ) to Joy" is nice and calm and mild, as far as music goes.
彼女は穏やかに眠っているようだった。
The woman seemed to be sleeping peacefully.