| TERM | DEFINITION | NOTES |
| adult | Anyone who already reached the age of majority. | The age of majority varies by country, but it ranges from 14 years to 21 years; for the purposes of AB/DL roleplay, an adult is at least 20 years old and cares for a child. |
| adult baby | An adult who roleplays as a baby. | The abbreviation is AB. |
| adult baby / diaper lover | Anyone who is an adult baby AND/OR a diaper lover. | The abbreviation is AB/DL. |
| baby | Anyone who is too young to be able to care for her- or himself by her- or himself. | For the purposes of AB/DL roleplay, a baby is less than 2 years old. |
| big | Anyone at least 12 years old but less than 20 years old. | For the purposes of AB/DL roleplay. |
| bottom | The rear of the diaper area, which includes the buttocks. | Bottom may sometimes denote the whole diaper area. |
| child | Anyone who did not yet reach the age of majority. | For the purposes of AB/DL roleplay, a child is an adult who is at least 20 years old and plays the role of a helpless child in a diaper. |
| comfy-cozy | Feeling pleasant all over, e.g. like a baby sleeping in a crib. | |
| crotch | The front of the diaper area. | |
| cum (noun) | Vaginal fluid (for females) or seminal fluid (for males). | See cum (verb) for more information. |
| cum (verb) | To excrete cum. | Cum is a regular verb; its past tense and past participle are both cummed. |
| diaper | A piece of clothing to wear on the bottom that catches pee-pee and poo-poo. | If it catches pee-pee and poo-poo, it counts as a diaper, even if one can push it down or pull it up all by her- or himself. |
| diaper area | The part of the body covered by a diaper, which includes the crotch, the private parts, and the bottom. | The abbreviation is DL. |
| diaper lover | Anyone who loves to wear, or go pee-pee or poo-poo in, a diaper. | |
| go | To excrete (pee-pee or poo-poo). | The syntax is go pee-pee or go poo-poo. |
| grown-up | See adult. | |
| little | Anyone less than 6 years old. | For the purposes of AB/DL roleplay. |
| middle | Anyone at least 6 years old but less than 12 years old. | For the purposes of AB/DL roleplay. |
| padded playdate | A playdate for two at which at least one wears a diaper. | |
| pee-pee | Liquid body waste from any animal. | Pee-pee is a noun; see go for the verb related to pee-pee. |
| peep | To go pee-pee. | Peep is a verb; see pee-pee for the noun. |
| peepy | Full of pee-pee. | |
| poo-poo | Solid body waste from any animal. | Poo-poo is a noun; see go for the verb related to poo-poo. |
| poop | To go poo-poo. | Poop is a verb; see poo-poo for the noun. |
| poopy | Full of poo-poo. | |
| potty | A toilet. | A child-size potty that it is impossible to flush, such as a potty chair, counts as a potty. |
| private parts | The genitals. | Private parts is usually used in the plural. |
| puff | Anything puffy, especially the padding in a diaper. | Please never use poof, because it is easy to mishear poof as poop. |
| puffy | Thick and squishy, especially like a sponge. | Please never use poofy, because it is easy to mishear poofy as poopy. |
| rump | See bottom. | |
| strut one’s puff | To show one’s diaper off, especially to show how puffy it is. | This is an idiom based on strut one’s stuff. |
| tushy | See bottom. | |