An ounce is an ounce of cannabis, referring to one ounce of the flower for purchase. An ounce is a lot of cannabis, regardless of how light it is. Think of one full ounce of weed as a Costco buy while an eighth of an ounce is more akin to a standard bag of chips from the drugstore. You could crush it in one sitting, but you're probably better off stretching it out through the week.
This website contains all the types of cannabis.
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