cough, n.
1. A percussive expulsion of air from the lungs, involuntary or deliberate; freq. occurring in series. See also: staccato, morse, the small broadcasts of a body learning weather.
2. In domestic architecture: the sound that reorganises a room. All other activities—dishes mid-rinse, emails mid-draft—become subordinate to the source. Cf. radius, cf. orbit.
3. (Of a child, at night.) A signal that translates roughly as: I am here, I am small, the world has edges I keep finding with my throat.
4. The unit of measure between one reassurance and the next. Three coughs = one hand on the back. Five = a glass of water carried like a lantern down the hall.
5. Archaic. From the Middle English coghen, imitative. Still imitative. Still the oldest language. Still the one that makes you put everything down.