I'm reading LLPSI, chapter 20 "Parentes" (skipping ahead quite a few chapters, just for a peek and to see how much I can understand from a more advanced chapter).
The third sentence reads:
Cūnae sunt lectulus īnfantis.
Why is lectulus (and the attached genitive īnfantis) in the singular, in apparent number mismatch with cūnae sunt?
Is it because lectulus īnfantis represents some single, abstract "concept of little bed" that all cribs are? Should it be transltaed into English as "Cribs are an infant's bed", in a similar vibe as "dogs are a man's best friend"?