Charterparty is a contract concluded between the shipowner and the charterer with the purpose to employ an entire vessel or some principal part of her for a voyage or series of voyages or for a period of time.
President of India v Metcalfe Shipping Co  1 QB 289, per Lord Denning M.R:
It seems to me that whenever an issue arises between the charterer and the shipowner, prima facie their relations are governed by the charterparty. The charterparty is not merely a contract for the hire of the use of a ship. It is a contract by which the shipowners agree to carry goods and to deliver them. If the shipowners fail to carry the goods safely, that is a breach of the contract contained in the charterparty; and the charterers can claim for the breach accordingly, unless that contract has been modified or varied by some subsequent agreement between the parties. The signature by the master of a bill of lading is not a modification or variation of it. The master has no authority to modify or vary it. His authority is only to sign bills of lading "without prejudice to the terms of the charterparty."
In Golden Ocean Group Ltd v Salgaocar Mining Industries PVT Ltd & Anor  EWCA Civ 265 per Lord Justice Tomlinson at para 22:
The conclusion of commercial contracts, particularly charterparties, by an exchange of emails, once telexes or faxes, in which the terms agreed early on are not repeated verbatim later in the exchanges, is entirely commonplace. It causes no difficulty whatever in the parties knowing at exactly what point they have undertaken a binding obligation and upon what terms. As Mr Young pointed out, it is often a matter of happenstance, or, metaphorically, the pressing of a button, whether a sequence of emails manifests itself in a single document as a thread or string of emails or in a series of individual documents.