1. When I entered the room, she was playing the piano.

1-1. When I entered the room, she played the piano.
1-2. As soon as I entered the room, she was playing the piano.

2. While I entered the room, she was playing the piano.

3. I entered the room while she was playing the piano.

4. I was entering the room while she was playing the piaon.

5. I was entering the room while I was reading a book.

6. I entered the room while I read a book.

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Are they all grammatical? Is #2 right?
What are the differences in meaning?
Does #1-1 mean #1-2? What is the meaning of 'while' in #4? Although, or however? Does #5 mean #6? What is the difference between them?

1-1. When I entered the room, she played the piano.

1-2. As soon as I entered the room, she was playing the piano.

These sound as if she started to play the piano when you entered the room, not that she was already playing and then you walked into the room.

Sentences 1 and 3 mean the same thing, and 2 and 4 are close.

Sentences 5 and 6 make me wonder -- were you reading and walking at the same time? "While" indicates simultaneous actions.

1. When I entered the room, she was playing the piano.

1-1. When I entered the room, she played the piano.
1-2. As soon as I entered the room, she was playing the piano.

These sentences are all grammatically correct and convey the same meaning. They indicate that at the time of your entry into the room, she was already playing the piano.

2. While I entered the room, she was playing the piano.

This sentence is grammatically correct, but it might sound a bit awkward. It suggests that you were in the process of entering the room while she was playing the piano.

3. I entered the room while she was playing the piano.

This sentence is grammatically correct and implies that you entered the room during the time when she was playing the piano.

4. I was entering the room while she was playing the piano.

This sentence is grammatically correct, and the word "while" here means "during the time" or "at the same time." It indicates that the action of entering the room and the action of playing the piano were happening simultaneously.

5. I was entering the room while I was reading a book.

This sentence is grammatically correct but may sound a bit strange. It suggests that you were in the process of entering the room while simultaneously reading a book. This combination of actions might not be common or logical.

6. I entered the room while I read a book.

This sentence is grammatically correct and implies that you entered the room at a specific point in time while you were already reading a book. The emphasis is on the completion of the action of reading the book upon entering the room.

In summary, all the sentences are grammatically correct except for #2, which sounds slightly awkward. The differences in meaning are subtle, with most sentences conveying the same general idea of the piano-playing happening at the time of entry. However, sentences #5 and #6 differ in terms of the combination of actions: #5 suggests simultaneous actions that may not be typical, whereas #6 implies a sequential relationship between reading the book and entering the room.

1. When I entered the room, she was playing the piano.

1-1. When I entered the room, she played the piano.
1-2. As soon as I entered the room, she was playing the piano.

These sentences are grammatically correct and convey the same meaning. In all these sentences, the action of playing the piano was already in progress at the time of entering the room.

2. While I entered the room, she was playing the piano.

This sentence is grammatically incorrect. "While" cannot be used in this context. A correct version of the sentence would be: "While I was entering the room, she was playing the piano." This sentence suggests that the action of entering the room and playing the piano were happening simultaneously.

3. I entered the room while she was playing the piano.

This sentence is grammatically correct and means that the action of entering the room occurred at the same time as the action of playing the piano.

4. I was entering the room while she was playing the piano.

This sentence is grammatically correct, and "while" here functions as a conjunction that means "during the time that." It suggests that the action of entering the room was happening at the same time as the action of playing the piano.

5. I was entering the room while I was reading a book.

This sentence is grammatically correct and suggests that the actions of entering the room and reading a book were happening simultaneously.

6. I entered the room while I read a book.

This sentence is grammatically correct and means that the action of entering the room occurred at the same time as the ongoing action of reading a book.

In summary:
- Sentences 1-1, 1-2, and 3 convey the same meaning.
- Sentence 2 is grammatically incorrect and needs to be rephrased.
- Sentence 4 suggests that the actions occurred simultaneously.
- Sentence 5 suggests that the actions occurred simultaneously.
- Sentence 6 suggests that the actions occurred sequentially, with reading a book happening first before entering the room.