whistle vs sign

whistle and sign both are nouns.

Word	Noun	Adjective	Verb	Adverb
whistle	Yes	No	Yes	No
sign	Yes	Yes	Yes	No

As nouns, sign is a hypernym of whistle; that is, sign is a word with a broader meaning than whistle:

whistle: the act of signalling (e.g., summoning) by whistling or blowing a whistle
sign: any nonverbal action or gesture that encodes a message

Other hypernyms of whistle include signal, signaling, signalling.

As verbs, sign is a hypernym of whistle; that is, sign is a word with a broader meaning than whistle:

Other hypernyms of whistle include signal, signalise, signalize.

whistle (noun)	sign (noun)
an inexpensive fipple flute	structure displaying a board on which advertisements can be posted
acoustic device that forces air or steam against an edge or into a cavity and so produces a loud shrill sound	a public display of a message
a small wind instrument that produces a whistling sound by blowing into it	a gesture that is part of a sign language
the act of signalling (e.g., summoning) by whistling or blowing a whistle	any nonverbal action or gesture that encodes a message
the sound made by something moving rapidly or by steam coming out of a small aperture	a character indicating a relation between quantities
	a perceptible indication of something not immediately apparent (as a visible clue that something has happened)
	a fundamental linguistic unit linking a signifier to that which is signified
	an event that is experienced as indicating important things to come
	(astrology) one of 12 equal areas into which the zodiac is divided
	having an indicated pole (as the distinction between positive and negative electric charges)
	(medicine) any objective evidence of the presence of a disorder or disease

whistle (adjective)	sign (adjective)
	used of the language of the deaf

whistle (verb)	sign (verb)
utter or express by whistling	be engaged by a written agreement
make a whining, ringing, or whistling sound	communicate silently and non-verbally by signals or signs
give a signal by whistling	mark with one's signature; write one's name (on)
move with, or as with, a whistling sound	make the sign of the cross over someone in order to call on God for protection; consecrate
move, send, or bring as if by whistling	communicate in sign language
make whistling sounds	place signs, as along a road
	approve and express assent, responsibility, or obligation
	engage by written agreement