古 gǔ rests on the mouth radical 口. The traditional reading of the graph, repeated in the dictionaries, is irresistible for a learner: a 十 (ten) above a 口 (mouth), the old as what ten mouths, ten generations, have passed down by word of mouth. Whatever the strict paleography, this folk-etymology captures the heart of the word exactly: 古 is not merely the distant in time but the inherited, the handed-on, what reaches us through many speakers across many years. The simplified and traditional forms are identical, five strokes unchanged.

From that core of what the generations have transmitted, three senses unfold:

1. Ancient, of old times. The far past as a stretch of time: 古代 gǔdài (ancient times), 古老 gǔlǎo (ancient, age-old), 远古 yuǎngǔ (remote antiquity), 自古 zìgǔ (since ancient times).
2. Classical, antique. The objects, texts, and traces the past left behind: 古典 gǔdiǎn (classical), 古文 gǔwén (classical prose), 古董 gǔdǒng (an antique), 古迹 gǔjì (a historic site), 考古 kǎogǔ (archaeology).
3. Quaint, unconventional. A person or manner that feels out of step with the present, old-fashioned in a slightly odd way: 古怪 gǔguài (eccentric), 古板 gǔbǎn (rigid and old-fashioned).

The thread is age that carries weight. To be 古 is to come down to us from before, whether as an era, an inherited treasure, or a temperament that belongs to an older world.

The first and broadest face of 古 is plain antiquity, the distant past as a span of time. 古代 gǔdài names that past as a historical era, the age of dynasties and classics, the default opposite of 现代 the modern. 古老 gǔlǎo is an adjective: not a date but a quality of great age, applied to a city, a craft, or a civilisation that has lasted. 远古 yuǎngǔ pushes further still, to the remote and almost legendary beginnings before recorded history. Together they sweep from the merely old to the unimaginably ancient.

From the past as time, 古 turns to the past as a body of things: the texts, objects, and traces antiquity has left in our hands. 古典 gǔdiǎn is the adjective for the classical, the canonical works and refined style of the old tradition. 古文 gǔwén is classical prose, the literary language of those works. 古董 gǔdǒng is the antique, the prized old object collected for its age. 古迹 gǔjì is the historic site, a ruin or monument that survives on the ground, and 考古 kǎogǔ is the discipline that digs such traces up and reads them. Here 古 is not abstract age but the concrete inheritance the past has handed down.

The third face of 古 turns inward, to character. When something belongs too much to an older world, it can seem out of step with the present, strange or stubbornly old-fashioned. 古怪 gǔguài pairs 古 with 怪 (strange) to mean eccentric or odd, a person or temper that does not fit ordinary expectation. 古板 gǔbǎn pairs 古 with 板 (stiff, a board) to mean rigid and inflexible, old-fashioned in a humourless way. In both, the antiquity that elsewhere lends dignity instead lends a faint sense of being left behind.

Hold the dictionary picture at the center of 古: a 十 (ten) standing over a 口 (mouth), the old as what ten mouths, ten generations, have handed down by speech. To be 古 is to reach us from before, carried across many speakers and many years.

From that one image the senses fan out. Let it be a span of time and you get antiquity: 古代 ancient times, 古老 the age-old, 远古 the remote past, 自古 since the beginning. Let it be the things the past handed down and you get the classical and the antique: 古典 the canonical, 古文 the old prose, 古董 the prized object, 古迹 the surviving site, 考古 the digging that reads them. And let it cling too tightly to a person and it turns to the quaint and the odd: 古怪 the eccentric, 古板 the inflexible. Whenever you meet 古, ask what age it carries, and whether that age lends dignity or simply leaves its bearer behind: 古往今来, throughout all the ages.