be`alim and adonim are also used as "singulars" and refer to people.
this has a very interesting development in mishnaic hebrew.
for those interested, see:
randall buth, "luk 19.31-34, mishnaic hebrew, and bible translation: is
kurioi tou pwlou singular?"
journal of biblical literature [104-4] 1985:680-685
shows unmistakable mishnaic texts with plural verbs used with these idioms
when having singualr meanings. includes biblical hebrew, lxx and aramaic
data.
fyi--still used today in modern hebrew "be`alim" = owner, though back to
biblical, singular grammatical concord.