penumbra /pe-numˈbrə/

1. A partial or lighter shadow round the perfect or darker shadow produced by an eclipse or by a large unfocused light source shining on an opaque object
2. The less dark border of a sunspot or any similar spot
3. The part of a picture where the light and shade blend into each other

penumˈbral adjective

• main planes
• mainprise
• mainprises
• main purpose rule
• mains
• mainsail
• mainsails
• main sequence
• mainsheet
• mainsheets
• mainspring
• mainsprings
• mainstay
• mainstays
• main store
• main stores
• main stream
• mainstream
• mainstreamed
• mainstreaming
• main streams
• mainstreams
• Main Street
• mainstreeting
• mainstreetings