Correct usage of "fine"

Question

"Fine" as an adjective means:

1. of very high quality; very good of its kind.
2. very thin or narrow.
3. [in Cricket] directed or stationed behind the wicket and close to the line of flight of the ball when it is bowled.

I found the following usage of the term "fine" in my textbooks, that say:

1. I am fine.
2. Fine adjustment screw [the part of microscope]
3. Throughout history, people have cut up the bodies of living things to find out what is inside. Their study was limited to what the eye could see, the fine details inside the organs were unknown.

Which sense (from the definitions mentioned above) does these three usages suggest?

Does saying "I am fine" really mean I am having high quality?

Doesn't that mean thin or narrow when I say "fine adjustment screw"?

How can a detail be of a highly quality when I say "...the fine details inside the organs."?

What are the other usage example of "fine"?

Answer 1

Look at the third instance of the word at merriam-webster.com.

The first example you provided fits definitions 6a and 6b for “fine”:

6 a : well or healthy : not sick or injured . feel fine

b : all right . that's fine with me

The second example fits definition 2-a-5:

2 a (1) : very thin in gauge or texture fine thread. (2) : not coarse . fine sand. (3) : very small . fine print (4) : keen . a knife with a fine edge (5) : very precise or accurate . a fine adjustment . trying to be too fine with his pitches

The third example fits definition 3:

3 : delicate, subtle, or sensitive in quality, perception, or discrimination . a fine distinction

There are more than three adjectival uses for the word “fine.”

Answer 2

Fine is usually an adjective, but in conversation you can also use it as an adverb. Fine has three main meanings. TFD

1. used to mean 'very good'

2. used to mean 'satisfactory'

3. used to mean 'small' or 'narrow'

It appears you have demonstrated all the senses in you question. Fine used in many sentences can be visited here: Oxford Dictionary