| Lewis base | |
| —n | |
| Compare Lewis acid a substance capable of donating a pair of electrons to an acid to form a covalent bond | |
| [C20: named after G. N. Lewis (1875--1946), US chemist] | |
| a scrap or morsel of food left at a meal. |
| a screen or mat covered with a dark material for shielding a camera lens from excess light or glare. |