word of the day: sidelight

The word of the day is sidelight:

noun

1. an item of incidental information.

2. either of two lights carried by a vessel under way at night, a red one on the port side and a green on the starboard.

3. light coming from the side.

4. a window or other aperture for light in the side of a building, ship, etc.

5. a window at the side of a door or another window. 

 

(https://www.dictionary.com/browse/sidelight)

 

 

"Then in 1969 came an unusual tree from Robert H. Whittaker, a plant ecologist at Cornell University for whom 'broad classification,' as he called it - numbering and delineating the kingdoms of life - was a sidelight."

 - David Quammen, The Tangled Tree: A Radical New History of Life