bawl definition: To bawl is defined as to cry or wail loudly. (verb) An example of bawl is to sob loudly upon hearing bad news. ...
Legality: A contract is a legal document and a PO is a commercial document. To elaborate, a PO is an offer from the buyer to the supplier. If accepted by the supplier (within a reasonable timeframe) the PO becomes a contract. Logically, this PO will have zero value if it's not accepted by the supplier.
With a Purchase Agreement, normally what you find is language that says that as long as the purchase order issued complies with the terms of the Purchase Agreement it is issued under, that order is binding and enforceable. The difference between the two has nothing to do with the time period involved. A Blanket Purchase Order may be for long period and a purchase agreement may be for a very short period. The difference has nothing to do with the volume involved.