sign vs communication

sign and communication both are nouns.

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

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

sign: a public display of a message
communication: something that is communicated by or to or between people or groups

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

sign: any nonverbal action or gesture that encodes a message
communication: something that is communicated by or to or between people or groups

sign (noun)	communication (noun)
structure displaying a board on which advertisements can be posted	something that is communicated by or to or between people or groups
a public display of a message	the activity of communicating; the activity of conveying information
a gesture that is part of a sign language	a connection allowing access between persons or places
any nonverbal action or gesture that encodes a message
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

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

sign (verb)	communication (verb)
be engaged by a written agreement
communicate silently and non-verbally by signals or signs
mark with one's signature; write one's name (on)
make the sign of the cross over someone in order to call on God for protection; consecrate
communicate in sign language
place signs, as along a road
approve and express assent, responsibility, or obligation
engage by written agreement