Slang and Mandarin commingle on the No. 7 line during the evening rush, and teenagers arrange their meeting spots by text on the N at Coney Island, the Wonder Wheel rising through train car windows at sunset.

At other times, on other lines, there are early appraisals of future company — “Dude, what does she look like?” is heard on a Friday in Brooklyn, with nightclubs waiting across the Williamsburg Bridge tracks — and assurances that, yes, someone will be home with dinner soon, as the No. 1 wheezes toward the Bronx.

The intermittently graphic particulars of a passenger’s phone chat with his roommate kept others rapt on a recent evening on the J train. He laughed. He snorted. He congratulated. Then he clicked off the phone and turned to his fellow travelers.

“They had sexual relations,” said the rider, Abbie Krinsky, from Bushwick, Brooklyn. “He just called me to let me know.”