Definition: an influence that works subtly to lighten or modify something
Usage: his sermons benefited from a leavening of humor
Similar words: imponderable
Definition: a factor whose effects cannot be accurately assessed
Usage: human behavior depends on many imponderables
Definition: a substance used to produce fermentation in dough or a liquid
Similar words: substance
Definition: a particular kind or species of matter with uniform properties
Usage: shigella is one of the most toxic substances known to man