travelling vs crossing

travelling and crossing both are nouns.

Word	Noun	Adjective	Verb	Adverb
travelling	Yes	No	No	No
crossing	Yes	No	No	No

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

travelling (noun)	crossing (noun)
the act of going from one place to another	a voyage across a body of water (usually across the Atlantic Ocean)
	traveling across
	(genetics) the act of mixing different species or varieties of animals or plants and thus to produce hybrids
	a path (often marked) where something (as a street or railroad) can be crossed to get from one side to the other
	a junction where one street or road crosses another
	a point where two lines (paths or arcs etc.) intersect
	a shallow area in a stream that can be forded