Print head
The moving part of a printer that actually lays the ink or strikes the character onto the paper.
Its shape follows the technology. In a dot-matrix printer it is a vertical column of tiny pins — 9 in the early ones, 24 in the better — fired at the ribbon to build characters from dots. In an inkjet it is a cluster of nozzles, often hundreds, metering droplets by the picolitre. Daisy wheel and typeball machines instead carry whole cast characters.
The head usually rides on a carriage that travels sideways along a rail while the paper advances line by line. Wear and clogging make it one of the parts most likely to fail; on inkjets the nozzles are sometimes built into the cartridge precisely so a fresh head arrives with every refill.