• Found this discussion in Duolingo, https://www.duolingo.com/comment/7135103.
  • Basically any possible "to be" in German.
  • "To be" translates into "sein". But "sein" is infinitive form. "Sein" has several from as explained in table below according to which is the subject.

./20161121-1753-cet-to-be-in-german-1.png