der Sohn

Der Sohn (the son) is masculine and takes der. The plural is die Söhne, formed with an umlaut plus an -e ending. That puts it in a different plural group from Bruder and Vater, which take -er or nothing at all, so the family words really do need to be learned one by one.

The word is used exactly as in English. Mein Sohn ist sechs Jahre alt means "my son is six years old". In casual family talk parents sometimes say Junge (boy) or use the child's name instead, but Sohn itself is neutral and works in any register.

Related family words follow familiar patterns. Der Schwiegersohn is the son-in-law, der Enkelsohn is a grandson (though der Enkel alone usually suffices), and der Stiefsohn is a stepson. The matching female forms replace Sohn with Tochter: die Schwiegertochter, die Stieftochter.

You will meet Sohn in surnames and in fixed expressions across German culture. Der verlorene Sohn is "the prodigal son", and older company names sometimes carry und Söhne (and sons), similar to English usage.

Pronunciation: Sohn is one syllable, [zoːn]. Two points matter here. The initial s before a vowel is voiced in German, so it sounds like an English "z". The oh is a long "o", and the h is silent, serving only to mark the vowel as long. The plural Söhne has two syllables and replaces that vowel with ö, made by saying "ay" with rounded lips.