German has three genders — der (masculine), die (feminine), das (neuter) — and most nouns just have to be memorized. But a handful of endings are (essentially) 100% reliable, unlike softer tendencies you may also know (e.g. "nouns ending in -e are usually die" — only about 90%). When you spot one of these endings, you can commit to the gender with confidence instead of guessing.

Always der (masculine)

Always die (feminine)

Always das (neuter)

So if you see -ung, it's die — every time (die Zeitung, die Wohnung, die Meinung...). Note -tum and -um overlap (a -tum word also ends in -um) — that's fine, both point to the same gender.

This only works when the ending is the noun's actual suffix, not just letters that happen to appear at the end — but for the vocabulary here, treat these as hard rules, not tendencies.