grammar → 之
TSUMUGU · TBCL 5 (est.) · 語法
grammar point · tier 1 · literary linker 之 (A 之 B = A's B, the classical 的)
· zhī
Literary linker: binds a modifier to a noun, the classical 的, kept in fixed and written phrases.

字源 FORM what the parts do

A foot (止) on the line (一), stepping off — the old word for to go. Grammar borrowed the going to carry the link from one word to the next; the it of classical lines (求之不得) rides the same foot.

故事 STORY a scene to remember it by

The foot steps off the first word and lands on the second, dragging a thread between them.
字源記憶法
框 · Frame
[modifier] 之 [noun]
觸 · Trigger
A modifier and its noun in a written or set phrase, where 的 would sound too plain.
序 · The move
1Place the modifier first, the head noun last.Could 的 stand in the same slot and mean the same thing?
2Set 之 between them.Is the phrase written, fixed, or four-character? If it is casual speech, switch back to 的.
例 · Examples
1父母陪孩子一起走過成長growing upof (literary 的)road
Parents walk the road of growing up alongside their child.
界 · Boundary
Same link, split by register: 之 is the literary and fixed-phrase linker (成長之路、三分之一); 的 is the everyday spoken one. Swap 之 into casual speech and it turns stiff; swap 的 into a set phrase and it breaks the phrase.
求之不得 之
Between two nouns 之 is the link of (A 之 B); after a verb the same foot is the classical it, the object pronoun (求之 = seek it).
✗ 這是我之書。 → ✓ 這是我的書。 (everyday speech takes 的, not 之)
✗ 成長的之路 → ✓ 成長之路 (one linker per slot; 之 already binds 成長 to 路, so 的 is redundant)
✗ 走過成長路 → ✓ 走過成長之路 (the linker is needed; bare juxtaposition drops the of)
English has one of for every register, so learners reach for 的 everywhere or 之 everywhere; the split is register, not meaning.