And the joke: A small medium at large.
For those of you wondering, I tried: Mecca, Meca, Mecah, Meccah, and Makkah.
For those of you not wondering, I also tried vegemite once. Love that stuff, even if it has nothing to do with this quiz.
"Micrometer" should be shown as the main answer, despite micron still being widely used (in English): The term micron and the symbol μ were officially accepted for use in isolation to denote the micrometre in 1879, but officially revoked by the International System of Units (SI) in 1967.