病 = 疒 + 丙. The outer frame 疒 (the sickness radical) is the semantic component, and 丙 (bǐng) sitting inside it is the phonetic. 疒 itself is a compressed picture: a person lying down (人) tipped against a low bed or couch, with two short strokes that older paleographers read as drops of sweat or as the lines of the bedframe. Wherever 疒 appears as a radical, the word concerns being unwell: 疼 (téng) ache, 痛 (tòng) pain, 疲 (pí) fatigue, 疯 (fēng) madness. It is one of the most semantically transparent radicals in the script.

The phonetic 丙 carries the sound and only the sound. In the old Heavenly Stems counting system 丙 is the third stem, and on its own it has no medical meaning; it was selected because its Old Chinese reading was close to the reading of 病. The Shuōwén Jiězì glosses 病 plainly as 疾加也, an illness that has worsened, distinguishing it from the lighter 疾 (jí). In the earliest texts 疾 is the ordinary ailment and 病 is the grave one, the sickness that has crossed into danger.

From the concrete sense of bodily sickness the character extended outward to anything wrong or defective. A flaw in an argument, a fault in a person's character, a bug in a machine: all can be a 病. This is the same move English makes when it calls a society "sick" or a plan "ailing." The radical keeps the body in view even when the subject is abstract, which is why 毛病 (máobìng) covers both a chronic cough and an annoying habit.

Japanese borrowed the character as 病 (byō / yamai) with the identical sickness radical, and it anchors the everyday word 病気 (byōki, illness) and 病院 (byōin, hospital). The Korean reading is 병 (byeong). Across the whole Sinographic world the glyph names the same thing: a body laid up on a bed, no longer whole.

See the radical 疒 as a low wooden bed leaned up on its side against a wall, a sick person stretched along it with two beads of sweat sliding off the frame. That tilted bed is the sickness radical, and it is the first thing your eye should catch in 病. Whatever sits inside the bed, the body is laid up.

Inside this one lies 丙 (bǐng), the third Heavenly Stem, doing nothing but holding the sound. Treat 丙 as a faceless lodger you cannot quite identify: it tells you how to say the word, bìng, in a sharp falling tone, like a doctor's clipped diagnosis. The 4th tone drop mirrors the patient sinking back onto the pillow.

Then watch the bed travel. Add a person and you get 病人, someone laid up on it. Add poison and you get 病毒, the unseen thing that put them there. Add a room and you get 病房, a hall of these beds in a row. Add fine hairs, 毛病, and the bed shrinks to a nagging little flaw that will not stay fixed. Every compound is just a new visitor to the same sideways sickbed.