Duration can be broken down into 6 parts: (1) total duration (2) onset (3) come up (4) peak (5) offset and (6) after effects. Depending upon the substance consumed, each of these occurs in a separate and continuous fashion.
These are catalogued as follows:
The total duration of a substance can be defined as the amount of time it takes for the effects of a substance to completely wear off into sobriety, starting from the moment the substance is first administered.
The onset phase can be defined as the period until the very first changes in perception (i.e. "first alerts") are able to be detected.
The "come up" phase can be defined as the period between the first noticeable changes in perception and the point of highest subjective intensity. This is colloquially known as "coming up."
The peak phase can be defined as period of time in which the intensity of the substance's effects are at its height.
The offset phase can be defined as the amount of time in between the conclusion of the peak and shifting into a sober state. This is colloquially referred to as "coming down."
The after effects can be defined as any residual effects which may remain after the experience has reached its conclusion. This is colloquially known as a "hangover" or an "afterglow" depending on the substance and usage.
It should be noted that the after effects of the substances listed on this site are not included as part of the total duration.