Diet as a noun normally refers to the food and drink consumed or to be consumed by a person. With no adjective attached to the word, it just means that. If there are adjectives or phrases attached to it, then there is a qualifier. Example, a bland diet means the food and drink consumed or to be consumed by a person is non-irritating to the intestines.
Diet as a verb such as “to diet” or “to be on diet” normally means to regulate, usually the amount, of food and drink consumed or to be consumed by a person.
Physicians have varied “ways” or “lingos” in ordering or prescribing diet for their patients. Here are some of the common ones that I am familiar with.
“Diet as tolerated” – consume any type and amount of food and drink that is tolerated.
“Small frequent feedings” – consume small amount of food and drink at a time or at any one time and this can be done at intervals shorter than that associated with the common way of eating three big meals a day.
“Bland diet” – consume food and drink that are not irritating to one’s intestines, such as not too spicy, not too oily, not too sour, cooked rather than raw foods, soft, and low in dietary fiber.
“Full diet or regular diet” – consume all types of food and drink that is well-balanced and capable of maintaining a state of good nutrition.
“Liquid diet” – consume a diet with no solid food intake and with replacement of solid food with liquids. Liquid diet may be clear liquid diet or full or general liquid diet. See below.
“Clear liquid diet” – consume a diet that consists of liquid food and drinks that are clear, meaning you can see through them. In this type of diet, you aren’t limited to colorless liquid food and drink; you are limited to food and drink that are clear. Example: apple juice has color , yet is still clear. Clear liquid diet consists of fluid foods that are easy to digest and leave little to no material in the digestive tract.
“General liquids or full liquids” – consume a diet that is made up only of fluids and foods that are normally liquid and foods that turn to liquid when they are at room temperature, like ice cream.
“Soft diet” – consume a normal diet limited to soft, easily chewable and digestible foods. This is usually prescribed to people who have difficulty chewing or swallowing.
Other types of diet prescription consist of therapeutic diet with specification of calories and/or contents, like low fat, high protein, low salt, etc.