I looked up the word "condition" in the dictionary, and it says that when it refers to a state or condition, it is an uncountable noun, so the phrase must be written as "in good condition." However, in the screenshot of the article I saw, which was highlighted in red, it was written as "in a good condition" and this phrase was also read as "in a good condition" by a native speaker in the accompanying audio. I did some searching on Google, and some people say that "in good condition" means that one's own state is good, whereas "in a good condition" has a different meaning, suggesting that the environment one is in is good. I want to know what the real situation is. Are "in good condition" and "in a good condition" really the same? Does "in a good condition" have a completely different meaning? This is really confusing to me. Thank you so much！[Image]

Question

Answer

In good condition and in a good condition mean the same.

They're both correct as the 'condition' can represent different things.

Without the article, condition could be 'shape' or 'health', for example.

The cat was in good shape.

The cat was in good health.

With the article, condition can mean 'state' or 'way'.

The cat is in a good state.

The cat is in a good state of health.

The cat is in a good way.

Whether or not we use an article depends on what we are using the word to represent, so it's useful to think about synonyms of a word if you're unsure about an article.

Answer

"Countable" vs. "uncountable" has nothing to do with your question because the phrase "in good condition" does not quantify "condition".  "Condition" is described as being "good", but "good" is not a quantifier. Countability only becomes an issue when you quantify something.

I can't think of an uncountable instance that quantifies "condition".  Using it that way might produce nonsense such as "much condition".  I can only quantify it in a countable way:
"He is in a good condition".
"He saw many patients who were in various conditions"

The phrase "in condition" should be understood as a common idiom, similar to
"in love"
"in shape"
"in health"
"in distress"
Some of these may be countable, uncountable, or either but countability has nothing to do with the meanings because the things are not quantified.

Answer

We usually use ‘in good condition’ for things, for example books and cars. It sounds wrong for a cat.

For ‘condition’ to be talking about the environment, we’d usually use the plural: ‘The conditions here are good.’ (The situation here is good)

We also use ‘condition’ to speak of health. His condition is improving. He has a heart condition.

The example isn’t the most natural phrasing, but it sounds ok. From the context, the health meaning is obvious.

Answer

They're the same;  'in good condition'  is used in formal and legal statements to refer to items, property, etc. being intact and undamaged.  If you return an item you have bought and claim a refund  i e  ask for your money back, the 'terms and conditions'* state that it should be 'in good condition'.  If someone is offering an item for sale they may describe it as being 'in good condition'. 
'In a good condition'  is more general, and can refer to people, animals, plants, etc. as well as objects.  It can mean that someone is not feeling well, or is injured or ill, as Bob the cat in your example.
*same word, different meaning - in this case the rules applying to returned goods