adder vs common viper

adder and common viper both are nouns.

Word	Noun	Adjective	Verb	Adverb
adder	Yes	No	No	No
common viper	Yes	No	No	No

As nouns, adder and common viper are synonyms defined as:

adder and common viper: small terrestrial viper common in northern Eurasia

Other synonyms of adder include Vipera berus.

adder (noun)	common viper (noun)
small terrestrial viper common in northern Eurasia	small terrestrial viper common in northern Eurasia
a machine that adds numbers
a person who adds numbers