An inch is a small unit of measurement. Twelve inches makes one foot.
You might get an inch of your hair cut off, or hem your jeans so they're an inch shorter. Some countries use centimeters and meters as units of measurement, but if you measure in inches, you can order a twelve inch pizza or print out three by five inch photos. When inch is used as a verb, it means "to creep slowly forward." The Old English version was ynce, from the Latin uncia, "a twelfth part."