penumbra

The partially shaded outer region of a shadow; an area of uncertainty or ambiguity.

• penumbral/pɪˈnʌmbrəl/(adj)半影的

• penumbra of
• constitutional penumbra
• penumbra of doubt
• in the penumbra

1. 1.The constitutional right to privacy exists in the penumbra of several amendments. (ambiguous border area)
2. 2.The village lay in the penumbra of the mountain's shadow, receiving only partial sunlight. (partial shadow)

• shadow/ˈʃædəʊ/— dark area
• fringe/frɪndʒ/— outer edge
• periphery/pəˈrɪfəri/— outer boundary

from Latin "paene" (almost) + "umbra" (shadow) — an almost-shadow, the gray zone between light and dark