Chinese omits 的 when:
– the relationship is institutional, official, or technical
– the two nouns form a recognized compound
– the phrase feels like a single unit rather than “A’s B”
When 的 is optional
的 is often omitted when the adjective is:
– a single, simple, descriptive adjective
– tightly bound to the noun
– forming a common phrase
Examples:
– 新书
– 大楼
– 小孩子
– 旧衣服
When 的 cannot be omitted.
- 她穿着漂亮的红色连衣裙。（descriptive）
红色 is a descriptive, multi‑syllable adjective; omitting 的 (红色连衣裙) is possible in some contexts, but with an additional adjective like 漂亮, 的 becomes required to keep the structure clear. - 他今天心情不太好的样子。（temporary）
Temporary or changeable states (心情好/不好, 生气, 累, etc.) almost always require 的 before the noun. - 我喜欢你做的那个特别的决定。（personal）
特别 expresses a subjective, personal evaluation; subjective adjectives normally require 的. - 这是我刚学的语法结构。（not a fixed compound）
语法结构 is not a tight, fixed adjective–noun compound, so 的 cannot be omitted after 刚学.
Quick diagnostic trick (4 steps)
- Is the adjective simple, objective, and monosyllabic?
If yes, 的 is often droppable.
If no (e.g., multi‑syllable, descriptive, emotional), 的 is required. - Is the adjective describing a stable, inherent quality?
If it’s a temporary or changeable state (累、开心、生气、心情好), 的 is required. - Is the adjective expressing a personal or subjective judgment?
If it’s evaluative (特别、奇怪、重要、糟糕), 的 is required. - Is the adjective–noun pair a fixed, tight compound?
If it’s not a common compound (e.g., 新手机, 大学生), 的 is required.