Definition of signs:
(n) :
(sometimes also used uncountably) A visible
indication; a clearly visible object, generally flat, bearing a short message in words or pictures
"their angry expressions were a clear sign they didn't want to talk."
(v) :
to
write one's
signature on (a document), thus showing authorship; to give legal consent by writing one's signature
"I forgot to sign that letter to my aunt."