California
Penal Code PC § 28200
As used in this article, the following words have the following meanings:
(a) “Purchase” means the purchase, loan, or transfer of a firearm.
(b) “Purchaser” means the purchaser or transferee of a firearm or the person being loaned a firearm.
(c) “Sale” means the sale, loan, or transfer of a firearm.
(d) “Seller” means, if the transaction is being conducted pursuant to Chapter 5 (commencing with Section 28050 ), the person selling, loaning, or transferring the firearm.