故 is a pictophonetic compound (形声字 xíngshēngzì): 古 gǔ (old, ancient) carries the sound, and 攵 pū (the strike radical, a variant of 攴, a hand holding a stick or rod) carries a sense of action done to something. The phonetic 古 is not silent here. It also leans on the page semantically, because 古 itself means "old, of long ago," and that meaning bleeds into nearly every sense 故 takes. The character keeps the same shape in simplified and traditional writing.

The Shuo Wen Jie Zi, the 2nd-century CE character dictionary, glosses 故 with 使为之也 (shǐ wéi zhī yě): roughly, "that which causes a thing to be done." This is the anchoring sense. A 故 is a cause, the settled reason that makes something happen. From that single root, the other senses fan out. Because a cause is something prior, something already established, 故 slides into "old, former, what was the case before." Because 攵 marks deliberate action upon something, 故 takes on "to do on purpose, deliberately." Used as a connective in classical prose, 故 means "for this reason, hence, therefore," literally pointing back to the cause just stated. And in the gentlest extension, the deceased are 故 because they belong now to what has passed.

The radical 攵 (also written 攴, called 反文旁 fǎnwénpáng in everyday Chinese because it resembles a reversed 文) appears in a large family of characters involving action, governance, or striking: 教 jiào (to teach), 政 zhèng (governance), 改 gǎi (to change), 攻 gōng (to attack), 收 shōu (to gather in). In each, something is acted upon. Within 故, the radical reminds us that a cause is not a passive fact but a force that makes things happen. In Japanese, 故 (ko in Sino-Japanese reading) survives in 故郷 (kokyō, hometown) and as the prefix 故 before a deceased person's name, exactly as in Chinese 故 plus a name.

The oldest and most literal sense of 故 is cause. When you ask 什么缘故 (shénme yuángù, for what reason) you are asking for the 故 behind an event, the thing that made it be. This sense survives intact in modern compounds: a malfunction is a 故障 (gùzhàng), literally an obstruction with a cause; an accident is a 事故 (shìgù), an incident with a cause behind it. The cause sense is also why 故 anchors the fixed phrase 无缘无故 (wú yuán wú gù), "without cause, for no reason at all," used when something happens with no traceable trigger.

Because a cause is something prior, 故 readily means "old, former, belonging to before." This is the most emotionally loaded family of the character. 故乡 (gùxiāng, hometown) is the native place one comes from and longs to return to, a word saturated with the literary tradition of homesickness. 故人 (gùrén) is an old friend from a former time. 故事 (gùshì) is a story, literally "old matters," the things that were, retold. And 故宫 (Gùgōng), the Old Palace, is the formal name of the Forbidden City in Beijing, the former imperial residence. In this family 故 overlaps closely with 旧 (jiù, old, worn): 故 leans toward "former, of a prior time," while 旧 leans toward "worn with use." A friend known long ago is 故人; a worn-out coat is 旧.

Two more senses round out the character. First, deliberateness: when 攵, the strike radical, brings its sense of willed action to the fore, 故 means "on purpose, deliberately." 故意 (gùyì) is the everyday adverb for doing something intentionally, and it carries a faint negative charge, since one usually accuses another of doing harm 故意 rather than praising a kindness done 故意. Second, the connective: in classical and formal modern prose, a lone 故 means "therefore, hence," pointing back to a cause just stated. This is the cause sense turned into grammar. A classical argument runs 因为A，故B (because A, therefore B). The literary 故 still surfaces in formal writing, legal language, and set phrases such as 故曰 (gù yuē, hence it is said).

Picture a hand with a rod tapping at something old. That is 攵, the strike radical, set beside 古, the ancient. The single image holds the whole character: a deliberate hand acting upon what is already old. From that one picture the five senses unfold like spokes. The thing the hand acts upon is a cause (缘故). What it taps is old and former (故乡, 故人, 故事). The hand acts on purpose (故意). Trace the rod back along the strike and you find the reason, so 故 also means therefore (因为A，故B). And the oldest things of all, those wholly past, are the dead (病故, 已故).

The discipline for a learner is to feel which spoke is active in a given compound. In 故乡 and 故事 the warmth of the former rules; the home and the tale are cherished, not blamed. In 故意 and 故弄玄虚 the willed hand comes forward, usually with a critical edge. In 故障 and 事故 the hidden cause is what matters, the fault to be traced. And the lone literary 故 is pure logic, the cause turned into a hinge between premise and conclusion.

Hold 故 against its near neighbor 旧. Both reach into the past, but 故 is the former, the prior, the cause-that-was, while 旧 is the worn, the used, the thing aged by handling. An old friend known long ago is a 故人; a coat worn thin is 旧. 温故知新 uses 故 because the old here is prior knowledge to be warmed over, not a worn object. When you meet 故, ask which thread the context has pulled: the cause behind, the time before, the will within, the hence that follows, or the life now wholly past.