die Schwester

Die Schwester (the sister) is feminine and takes die. The plural is die Schwestern, formed by adding -n. There is no umlaut here, which sets it apart from Mutter and Vater, so the family words do not all behave the same way.

German has a useful word that English lacks: die Geschwister means "siblings" and covers brothers and sisters together. It exists only in the plural, so you say ich habe zwei Geschwister (I have two siblings) and never use a singular form of it.

Schwester has a second everyday meaning: it is the traditional word for a nurse. Die Krankenschwester is the full form, but in a hospital patients and staff often shorten it to Schwester, sometimes with a first name attached, as in Schwester Anna. The gender neutral term Pflegefachkraft is now official, though Krankenschwester remains widely used in conversation.

Common compounds include die Halbschwester (half sister), die Schwägerin (sister-in-law, which does not contain Schwester at all), and die Schwesterfirma (sister company). The adjective schwesterlich means sisterly, though it appears far less often than its English equivalent.

Pronunciation: Schwester is [ˈʃvɛstɐ], three sounds that beginners often get wrong at once. The sch is an English "sh", the w sounds like a "v", and the final -er is soft, closer to "uh". So the word comes out roughly as "SHVES-tuh", with the stress on the first syllable.