The correct use of the term "TLS session" TLS consists of sub-protocols including the handshake where the key-exchange is and the record protocol. If I want to use a statement like: 


  both parties negotiate a ciphersuite that defines the algorithms that
  will be used in the session


Is this a correct statement? Can I use the term session in a context that includes the key-exchange? The term session gives me the impression that it is after the key-exchange has been done. However, I use it in my statement because I am not sure if the ciphersuite defines anything beyond the key-exchange? 

Need more clarifications please.
Yes, that looks like a correct usage of the word session.

Of course the session keys are only valid for the record layer. But the session keys are tied to the session, not the other way around. And usually the TLS session is of course tied to a TCP/IP session, but that doesn't need to be the case.