duck's egg vs duck

duck's egg and duck both are nouns.

Word	Noun	Adjective	Verb	Adverb
duck's egg	Yes	No	No	No
duck	Yes	No	Yes	No

As nouns, duck's egg and duck are synonyms defined as:

duck's egg (noun)	duck (noun)
(cricket) a score of nothing by a batsman	small wild or domesticated web-footed broad-billed swimming bird usually having a depressed body and short legs
	a heavy cotton fabric of plain weave; used for clothing and tents
	flesh of a duck (domestic or wild)
	(cricket) a score of nothing by a batsman

duck's egg (verb)	duck (verb)
	avoid or try to avoid fulfilling, answering, or performing (duties, questions, or issues)
	to move (the head or body) quickly downwards or away
	submerge or plunge suddenly
	dip into a liquid