II vs span

II and span both are nouns.

Word	Noun	Adjective	Verb	Adverb
II	Yes	No	No	No
span	Yes	No	Yes	No

As nouns, span is a hyponym of II; that is, span is a word with a more specific, narrower meaning than II:

II: the cardinal number that is the sum of one and one or a numeral representing this number
span: two items of the same kind

Other hyponyms of II include craps, snake eyes, brace, couple, couplet, distich, duad, duet, duo, dyad, pair, twain, twosome, yoke.

II (noun)	span (noun)
the cardinal number that is the sum of one and one or a numeral representing this number	the act of sitting or standing astride
	a structure that allows people or vehicles to cross an obstacle such as a river or canal or railway etc.
	the distance or interval between two points
	a unit of length based on the width of the expanded human hand (usually taken as 9 inches)
	two items of the same kind
	the complete duration of something

II (verb)	span (verb)
	to cover or extend over an area or time period