German words ending in -o

German does not build words with -o. Every noun on this page arrived from somewhere else, either as a loan (das Kino, das Radio, das Studio, das Konto) or as a clipping of a longer word (das Auto from das Automobil, das Kilo from das Kilogramm). That is the whole pattern: a foreign noun with no obvious German home tends to land in das.

The clippings are the useful half. A short form usually keeps the gender of the word it was cut from, so you can often work it out instead of memorising it. That is also what predicts the exceptions: die Disco is short for die Diskothek, so it is die. Der Zoo is what is left of der zoologische Garten, so it is der.

Usually is the right word there, because the pull of the other -o words can win. Das Foto was cut from die Fotografie and went neuter anyway, which makes it the case that shows the working out is a help rather than a guarantee.

For the exam, guess das and take the odds. The words are common, they are short, and in this deck the ones that break the pattern are few enough to name. One outside it deserves naming too. Der Euro is masculine, and you will say it more often than any other noun on this page.