Commutative- equivalent consideration
Aleatory- not equivalent consideration
Executory- not yet, gagawin palang
Executed- has delivered, has paid, performed
Accessory- Not stand alone, dependent of principal
Principal- can stand alone
Formal (solmn)- form required
Informal (common or simple)- no form required
Onerous- reciprocally obligated
Gratuitous- Free, donation
Remuneratory- Compensate the person