Diet (noun)

1. A regulated intake of food, especially for health or weight-loss reasons.
2. A specific set of foods or a meal plan, especially as prescribed by a physician.
3. The typical or normal food consumed by an individual or group.
4. A limited or restricted intake of food for a particular purpose.
5. A way of life that emphasizes healthy eating habits.

Origin:

The word "diet" comes from the greek word "diaita", which means "way of life". in the 15th century, it came to mean "a controlled intake of food for medical or health reasons".

Examples:

1. She's been on a strict diet to lose weight.
2. He follows a vegetarian diet for ethical reasons.
3. The athlete needs to stick to a high-protein diet.
4. Her doctor prescribed a low-fat diet for her heart health.
5. The school is promoting a healthy diet for the students.