In this case 'define' means to describe the nature, properties, or essential qualities of something. This is different to "consist of" ,"be made up of" and "include". You can say that various medicines consist/ are made up of/include various ingredients.

correct: "such as" incorrect: "such like" The word "define" has several different meanings. One of them is "To describe the nature or basic qualities of" (taken from thefreedictionary.com) Examples: "A willingness to work hard defines a successful student." This means that a basic characteristic of a successful student is the willingness to work hard. Therefore, in your post, "something" is an essential characteristic or quality of "part A and part B." That is, something "defines" part A and part B.

When you think of "define" think of "definition". For example, the definition of "fast" is to move quickly. However, when you use "consist of", "be made up of" and "include" you are speaking of ingredients or parts or qualities. A few examples: 1. A sandwich consists of bread, sandwich meat, lettuce, tomato and mayonnaise. 2. The human body is made up of blood, bone, muscles and ligaments. 3. A nice person has the following qualities: Compassion, kindness, respect.