CARLEY, Justice.

Bobby Jones Jackson was charged with purchasing marijuana in violation of OCGA § 16-13-30 (j) (1). Under OCGA § 16-13-30 (j) (2), conviction of this crime would result in felony sentencing even though the amount of marijuana that Jackson allegedly purchased is less than one ounce. Under OCGA § 16-13-2 (b), a conviction of possession, rather than purchase, of this small amount of marijuana would mandate only misdemeanor punishment. Based upon the disparity between the prescribed punishments for possession and purchase of the same amount of marijuana, Jackson filed a demurrer asserting the unconstitutionality of OCGA § 16-13-30 (j) (2). The trial court sustained the demurrer and dismissed the indictment. From this order, the State appeals directly pursuant to OCGA § 5-7-1 (a) (1).

The initial consideration in an equal protection challenge to a criminal statute is whether the defendant is similarly situated to members of a class who are treated differently than he. Reed v. State, 264 Ga. 466 ( 448 S.E.2d 189) (1994). Therefore, Jackson was required to show that those who purchase less than one ounce of marijuana are similarly situated to those who possess that same amount of contraband. Criminal defendants are "similarly situated" for purposes of equal protection "only if they are charged with the same crime or crimes." Woodard v. State, 269 Ga. 317, 321-322 (3) ( 496 S.E.2d 896) (1998). Under OCGA § 16-13-30 (j) (1), the purchase of marijuana is set forth as a separate unlawful act from the possession of that controlled substance. The meaning of "purchase" is "to obtain by paying or promising to pay a price. [Cits.]" Northeast Factor Discount Co. v. Mortgage Investments, 107 Ga. App. 705, 709 (1) (c) ( 131 S.E.2d 221) (1963). "Possession," on the other hand, is defined as "the right to exercise power over a corporeal thing. . . . [Cits.]" Cook v. State, 136 Ga. App. 908, 909 (2) ( 222 S.E.2d 656) (1975). Thus, a purchase of drugs connotes the act of engaging in a commercial transaction, which is not an element of the act of simply possessing the contraband. This is a viable distinction, since commercial drug transactions can pose a greater threat to the public health, safety and welfare than the private possession of the same controlled substance. See Tillman v. State, 260 Ga. 801, 802 ( 400 S.E.2d 632) (1991).

Because OCGA § 16-13-30 (j) (1) provides that the purchasers of marijuana commit a different crime than do the possessors of that contraband, Jackson cannot base his challenge to the constitutionality of the felony punishment prescribed for his alleged commission of the former offense upon the General Assembly's determination to provide a misdemeanor sentence for those who only possess the same amount of the contraband. For equal protection purposes, only those defendants charged with purchasing marijuana are similarly situated to Jackson. Woodard v. State, supra at 222 (3). There is no contention that, unlike others charged with the purchase of less than one ounce of marijuana, Jackson faces harsher punishment. Compare Phagan v. State, 268 Ga. 272, 274 (2) ( 486 S.E.2d 876) (1997) (statute imposing greater punishment for same crime on the basis of the defendant's age). The imposition of a felony sentence applies equally to all those accused of purchasing any amount of the controlled substance and, thus, there is no unconstitutional disparate treatment of similarly situated persons. Sims v. State, 260 Ga. 782, 783 (1) ( 399 S.E.2d 924) (1991). Thus, the trial court erred in sustaining Jackson's demurrer and dismissing the indictment charging him with the purchase of marijuana.

Judgment reversed. All the Justices concur.

DECIDED APRIL 12, 1999.