mucus

"I got a letter from my brother."

"to line troops"

"The doctor examined the patient's nasal passages for any signs of mucous discharge. "

"Bark has a rough feel."

"The children were running to catch the school bus. "

"The sweat on my forehead was a secretion caused by the hot weather. "

"The wild pitch bounced and hit the catcher in the throat."

"The bad news about the project was a real down for the team. "

"The membranes of our cells allow nutrients in and waste products out. "

"Listening to the tap next door drip all night drove me mad!"

"Oily substances render things slippery."

"She has a cold in the nose."