3, 18-19 years, 20-24 years, 20-25 years, 20s, adolescence, adolescent, adolescents, attitude, bonded, bonding, buddies, buddy, caucasian ethnicity, caucasians, color, color image, colored, colors, colour, colours, companionship, comrade, comrades, cool, cool attitude, dark, diversity, few, friend, friendliness, friendship, friendships, generation z, groups, hang out, hanging out, hanging out together, horizontal, horizontally, horizontals, human, human being, humans, immature, immaturity, indoor, indoors, inside, juvenile, juveniles, kids, lifestyle, lifestyles, looking away, looking over shoulder, man, mass transit, men, minor, minors, mixed race people, mixed race person, multi ethnic group, multi-ethnic group, multi-racial, pal, pals, people, person, photographic, photography, puberty, pubescence, pubescent, rapid transit system, spending time, standing, stood, subway, subways, teen, teenage, teenager, teenagers, teens, three, three people, together, togetherness, transit, transport, transports, underground, whites, woman, women, young, young adult, young men, young women, youth, youthful, youthfulness, youths, europe, germany, western europe, western european