Do you mean preposition? And "be" is not a preposition. Propositions are diff than parts of speech though. :~]
The word proposition is a noun, a singular, common, abstract noun, a word for a plan or proposal; and a verb (proposition, propositions, propositioning, propositioned).
The word used to introduce a formal debate proposition is "resolved."
Citizens made a proposition to build a playground for the kids.
I don"t know what a proposition is.
No, it is a proposition.
I'll make you a proposition: if you'll buy a dictionary, I'll give you the answer.
Naysayers
A couple of months ago law makers made propositions OR I voted no on proposition 8
subject, theme, issue, proposition
God's proposition.
difference between a proposition and non proposition
The debatable proposition was argued for over three hours.