"male" principle, light, sun
阳 centers on the bright, active, masculine principle in Chinese philosophy, often associated with the sun and light.
阳 is the simplified form of 陽, combining ⻖ (hill, mound) with 日 (sun) to suggest the sunny side of a hill, representing the bright yang principle.
The hill ⻖ catches the sun 日 on its bright side: that is the yang, the light, male principle.
For ヨウ, imagine the sun shining on a hill and someone saying 'Yo!' to greet the bright morning: Yo -> ヨウ.