Limits in a scene may be for practical reasons, such as:
- No sexual intercourse---such as when you're not familiar with the person with whom you are playing BDSM-wise and don't want to risk a sexually-transmitted disease (STD), or when you don't want to get pregnant,
- No breaking of skin because you don't want the risk of infection or scarring which can or will occur during cutting, flogging, piercing, whipping, and so on, or
- No bruising---such as when you're a bikini or fashion model; or because your husband/wife doesn't know you are into BDSM and you don't want them to suspect.
Some limits may be psychological, or may be related to your beliefs or to experiences you have had in the past. These limits may apply to:
Some limits may be related to physiological or medical conditions, such as:
- Heart issues,
- Joint or muscle problems,
- High or low blood pressure, or
Some limits may be related to fear, such as:
- Claustrophobia, or
- Fear of hypodermics.
Other limits may be purely related to endurance or tolerance. In this case the bottom will usually signal their partner with a safeword or action when a limit is being approached, or when the bottom needs their partner to slow down or reduce the intensity of what they're doing (e.g., flogging).
Hard limits are limits which are absolutely non-negotiable. Medical or physiological limits are obvious examples of hard limits. "No fucking, I'm married", or "no cutting, I'm a professional model" are also usually hard limits.
Soft limits are limits which may be negotiable. These can be limits which the person you're playing with you needs you to respect, but later on in the play ask again because they may have changed their mind. Alternatively, a soft limit today may be no limit tomorrow once your partner becomes more comfortable with you.