Nominal: In this level of measurement, alphanumeric characters or names are used to categorize the data. For example, if gender is your variable, the responses will be male or female.
Ordinal: Ordinal level variables have a meaningful order to them such as rank. For example there is an order to “drink size” (small, medium, large, extra large), however there is not a consistent interval (volume, distance, time, etc.) among categories.
Scale: Numeric variables that have equal intervals between each value, for example age. For example, the amount of time between a 1 year old and 2 year old is the same amount of time as a 51 and 52 year old.