小 (shō) means “small size, small” | MotiTan Japanese Dictionary

More examples

ジュースは小にします。jū su wa shō ni shi ma su

I'll have a small juice.

この店では、ケーキを小で注文できます。ko no mise de wa kē ki o shō de chū mon de ki ma su

At this restaurant, you can order a small cake.

Identifies the smaller available size or amount of something.

ミニmini: A small size or amount offered as an option.
小盛りkomori: A serving made smaller than the standard amount.

物の大きさや分量などが小さいこと。mono no ō ki sa ya bun ryō na do ga chii sa i ko to

小 (shō, "small") is the Sino-Japanese reading of the kanji 小, whose basic meaning is small.

In drink orders, 小 (shō, "small") commonly contrasts with 中 (chū, "medium") and 大 (dai, "large") on size menus.