while vs cold spell

while and cold spell both are nouns.

Word	Noun	Adjective	Verb	Adverb
while	Yes	No	No	No
cold spell	Yes	No	No	No

As nouns, cold spell is a hyponym of while; that is, cold spell is a word with a more specific, narrower meaning than while:

while: a period of indeterminate length (usually short) marked by some action or condition
cold spell: a period of cold weather

Other hyponyms of while include cold snap, hot spell, snap.

while (noun)	cold spell (noun)
a period of indeterminate length (usually short) marked by some action or condition	a period of cold weather