The willingness of an individual backed up with purchasing power at a given time is

The concept you are referring to is effective demand. Let me explain it to you in a straightforward way:

Demand: Generally, demand refers to the desire or willingness of a consumer to purchase goods or services. However, just having the desire is not enough. Demand becomes impactful only when it is supported with the capability to purchase.

Effective demand: This is more than just a simple desire or demand. It represents the situation where an individual not only wants to purchase a product or service but also has the actual purchasing power to do so. This means they have the money or resources to back up their desire at a given time.

Desire: This term simply denotes a wish or want, without any implication of capability to fulfill it. For instance, many people might desire a luxury car, but not everyone can afford it.

Utility: This is a different concept entirely, referring to the satisfaction or benefit a consumer receives from consuming a product or service. It does not necessarily align with the ability to purchase.

In summary, when discussing the willingness to buy something and having the funds ready at that moment, it's referred to as effective demand because it combines the desire with the actual capacity to fulfill that desire.