periscope vs sub

periscope and sub both are nouns.

Word	Noun	Adjective	Verb	Adverb
periscope	Yes	No	No	No
sub	Yes	No	Yes	No

periscope (noun)	sub (noun)
an optical instrument that provides a view of an otherwise obstructed field	a submersible warship usually armed with torpedoes
	a large sandwich made of a long crusty roll split lengthwise and filled with meats and cheese (and tomato and onion and lettuce and condiments); different names are used in different sections of the United States

periscope (verb)	sub (verb)
	be a substitute