When a monosyllabic adjective is used attributively for the purpose of making a distinction, 的de is needed. This means there are at least two of the same item in the situation.
jiā lǐ yǒu liǎng gè píng guǒ ﹑liǎng gè táo zǐ 。mā mā shàng wǔ bǎ dà de píng guǒ gěi le wǒ ，suǒ yǐ xià wǔ jiù gěi wǒ xiǎo de táo zǐ 。
There were two apples and two peaches at home. My mother gave me the bigger apple in the morning, so she gave me the smaller peach in the afternoon.
(大 and 小 are both monosyllabic; 大的 and 小的 are used because ‘big’ and ‘small’ are used to distinguish the two apples and the two peaches.)
(Situation: A photographer is arranging a group of people to be in a photo.)
gāo de rén zhàn hòu miàn ；ǎi de rén zhàn qián miàn 。
Taller people stand at the back; shorter people stand in front.
(高人 and 矮人 would be incorrect.)
 Yip, P. C., Rimmington, D., Xiaoming, Z., & Henson, R. (2009). Basic Chinese: a grammar and workbook. Taylor & Francis.