1. I made up my mind to stop playing computer games.

2. I made a decision to stop playing computer games.

3. I made decisions to stop playing computer games.

4. I made a determination to stop playing computer games.

5. I made determinations to stop playing computer games.

[Are they all the same in meaning? Can we use 'determination' instead of 'decision'? What about the plural forms, decisions or determinations?]

1 and 2 mean the same thing.

The others are close, but are not commonly used. If you were to say, "I was determined to stop playing computer games," then you'd be close to the meaning in 1.

1. "I made up my mind to stop playing computer games." - This sentence means that you have firmly decided or resolved to stop playing computer games. It implies a personal conviction or determination.

2. "I made a decision to stop playing computer games." - This sentence also conveys that you have made a conscious choice or resolution to stop playing computer games. It is similar in meaning to the first sentence but uses a more formal phrasing.

3. "I made decisions to stop playing computer games." - In this sentence, the plural form of "decisions" is used, suggesting that you have made multiple individual decisions at different times to stop playing computer games. It indicates a repeated or ongoing process of decision-making.

4. "I made a determination to stop playing computer games." - This sentence means that you have made a strong and resolute decision to put an end to playing computer games. It emphasizes a sense of perseverance and resolve.

5. "I made determinations to stop playing computer games." - Similar to the third sentence, this sentence uses the plural form of "determinations," indicating multiple instances of making determined choices. It conveys a sense of dedication and commitment to stop playing computer games.

In terms of meaning, all the sentences convey the idea that a decision has been made to stop playing computer games. However, slight differences in nuance and emphasis exist between them.

You can use "determination" instead of "decision" to convey a stronger sense of resolve and perseverance. Both are suitable choices, but "determination" tends to evoke a stronger sense of willpower and commitment.

Regarding the plural forms, using "decisions" or "determinations" depends on whether you want to express a singular decision or multiple decisions made at different times. "Decisions" suggests a repeated or ongoing process, while "determinations" implies multiple instances of resolute choices.