addendum
- n textual matter that is added onto a publication; usually at the end
adder
- n a person who adds numbers
- n a machine that adds numbers
- n small terrestrial viper common in northern Eurasia
adder's fern
- n mat-forming lithophytic or terrestrial fern with creeping rootstocks and large pinnatifid fronds found throughout North America and Europe and Africa and east Asia
adder's tongue
- n ferns with fertile spikes shaped like a snake's tongue