GC: n

S: WHO – http://www.who.int/mediacentre/factsheets/fs360/en/ (last access: 2 May 2017); https://www.nhlbi.nih.gov/health/health-topics/topics/copd/signs (last access: 2 May 2017).

N: 1. Early 13c., “gesture or motion of the hand,” especially one meant to communicate something, from Old French signe “sign, mark,” from Latin signum “identifying mark, token, indication, symbol; proof; military standard, ensign; a signal, an omen; sign in the heavens, constellation,” according to Watkins, literally “standard that one follows,” from PIE *sekw-no-, from root *sekw- “to follow.”
2. Any objective evidence of disease, as opposed to a symptom, which is, by nature, subjective. For example, gross blood in the stool is a sign of disease; it is evidence that can be recognized by the patient, physician, nurse, or someone else. Abdominal pain is a symptom; it is something only the patient can perceive.
3. An objective evidence, manifestation, symptom in abnormality discoverable on examination of a patient.
Example: Calcification of the coronary arteries is a specific sign of atherosclerotic disease.
4. Collocations (sign: sth that shows that sth exists/may happen):

• Adj.: clear, definite, distinct, obvious, real, sure, telltale, unmistakable | external, outward, visible All the outward signs of growth in the market are there. | tangible | early, first Strong likes or dislikes of various foods are another of the early signs of pregnancy. | increasing | encouraging, good, healthy, hopeful, positive, welcome He was silent. It was a good sign. | bad, disturbing | danger, ominous, warning Are appliances you buy safe? We point out the danger signs.
• Verb + sign: bear, have The murder had all the signs of a crime of passion. | exhibit, display, give, show By now the fish was showing signs of distress. | detect, find, see, watch out for We detected signs that they were less than enthusiastic about the holiday. | interpret (sth as), read, recognize, see sth as | look for Look carefully for signs of damp. | point out.
• Sign + verb: appear, come The first signs of spring appeared. | indicate sth, point to sth All the signs pointed to it being more than just a coincidence.
• Prep.: at a/the ~ He disappeared at the first sign of trouble. | from ~ The villages regarded the earthquake as a sign from God. | ~ of.
• Phrases: sign of life There was no sign of life in the house (= there seemed to be nobody there). | a sign of the times It’s a real sign of the times: 30 small businesses face financial ruin this month. | little/no/not the least/not the slightest sign (of sb/sth) He spoke up without the slightest sign of nervousness.

S: 1. OED – http://www.etymonline.com/index.php?term=sign (last access: 2 May 2017). 2. http://www.medicinenet.com/script/main/art.asp?articlekey=5493 (last access: 2 May 2017). 3. TERMIUM PLUS – http://goo.gl/5lYVYn (last access: 2 May 2017). 4. OD – http://oxforddictionary.so8848.com/search1?word=sign (last access: 2 May 2017).

SYN:
S:

CR: symptom, symptomatology, syndrome.