Various terminologies pertaining to measurements

I am trying to find appropriate names for various components related to measuring something. For instance, given the following sentence:
100 kg of flour

I am able to come up with the following:

• 100 represents quantity/amount
• kg represents a unit of measurement/measure unit
• 100 kg represents a metric

But I struggle with appropriate naming for:

• Weight/mass -> the thing being measured
• Flour -> the thing undergoing the measurement

What is good, concise vocabulary to denote such terms?

Kindly take note that I am looking for vocabulary that applies to as many different contexts of measuring as possible. For this purpose, I am coining the following examples:

1. A person undergoing a psychiatric evaluation. This evaluation on an abstract level can be said to measure the sanity of a person. In this case; we have the following meta components:

   • Patient -> The person under evaluation; e.g. the thing undergoing the measurement
   • Patient’s mental state -> the thing being measured
   • sane, insane, depressed, traumatized -> the qualitative scale representing the metric involved
   • Psychiatrist -> The assessor/evaluator/measurer

2. A person taking an IQ test. This is supposed to measure a person’s intelligence; or more specifically the g-factor. Again, the components on an abstract level would be:

   • Person taking the test -> the thing undergoing the measurement
   • g-factor of a person -> the thing being measured
   • score -> a relative metric

3. A doctor testing out the effectiveness of medication on a volunteer. Again the components here are:

   • Patient —> the thing undergoing the measurement
   • effectiveness of the medication –> The thing being measured

4. Kinematic viscosity of oil

   • Oil -> the thing undergoing the measurement
   • Kinematic viscosity –> The thing being measured
   • centiStokes —> Unit of measurement

In all of the above different scenarios, we can abstract away from the specific context of a psychiatric evaluation, IQ evaluation, medical evaluation, oil quality evaluation to that of the general context of measuring something. In all of those instances; as applies; we can map specific terminologies to:

1. amount/quantity/magnitude
2. unit/measure unit
3. metric
4. The thing being measured
5. the thing undergoing the measurement

What are good, concise names for 4 and 5?

PS:

1. I may have made some mistakes in any of the above mappings; if so then kindly guide me accordingly in the comments.
2. I was motivated to ask this question here by: Terminology for expressing the scale of a measurement system. However, it could be that in the general English vocabulary that there are no suitable terms to speak about 4 and 5 in a more concise way than I already employed. In such a case, I would be willing to borrow technical terminologies. My assumption is that scientists have developed their own specific vocab to denote the above. If you have knowledge of such specific vocab then that would be welcome as well.