The phrase "a sign of affection" is correct and usable in written English.
You can use it to describe any type of gesture or behavior that expresses love and/or fondness for someone or something. For example, "The caress of his hand on her cheek was a sign of affection."
When I expressed the opinion that my horse's bumping me gently with his head was a sign of affection, he said, "Affection?
I shouldn't be mad because these nicknames are a sign of affection.
Young lovers in ancient Greece hung wreaths on their lovers' doorways as a sign of affection.
Some have given me this name of Meyer Lansky, the Jewish mobster, as a sign of affection.
"Nobody hissed at me, and two of them were blowing bubbles, which is a sign of affection," he said.
Jack Martini, a former manager at the station, said he had left the receivers on as both a sign of affection and — he hoped — of possible preservation.
The men, in the main, she says, were hardcore misogynists, who hated not having sexual access to the women, and would become deeply offended at any sign of affection between them.
The fact that the crowd screamed and waved flags around the couple shows how far we have come since the days when the tabloids were expressing outrage at any sign of affection between lesbians on TV.
The only time Da and Mother show any sign of affection is when young Charlie is flying off to his wedding and they stand outside their front door waving him off.
To give a whole home-baked black cake as a gift, Ms. Marshall said, is a sign of great affection and intimacy.
In genre fiction, making your city look bad is a sign of deep affection — which is precisely the message conveyed in new books by two Chicago writers.
