1. I will visit my uncle tomorrow.

2. I visit my uncle tomorrow.
3. I am visiting my uncle tomorrow.
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Are they all grammatical? Does #2 mean #1 in meaning? Are #2 and #3 grammatical? Are they all the same in meaning?

Yes, all three sentences are grammatically correct.

However, the meanings of the sentences differ slightly:

1. "I will visit my uncle tomorrow" expresses a future action, implying that you have made plans to visit your uncle and intend to do so.

2. "I visit my uncle tomorrow" suggests a habitual or regular action. It implies that you typically visit your uncle on a certain day or at a specific time, and tomorrow happens to be one of those days.

3. "I am visiting my uncle tomorrow" indicates a planned action that will take place in the near future. This sentence implies that you have already arranged to visit your uncle and will do so tomorrow.

While the main idea is the same -- visiting your uncle -- the way in which it is expressed differs slightly in terms of the tense or intention.

They are all grammatical and mean the same.

Yes, all three sentences are grammatically correct.

In terms of meaning, there are slight differences between the sentences:

1. "I will visit my uncle tomorrow." - This sentence indicates a future action. It implies that you have made a decision or have a plan to visit your uncle tomorrow.

2. "I visit my uncle tomorrow." - This sentence is a simple present tense statement. It suggests that visiting your uncle is a regular occurrence or something that you typically do, and it specifically refers to the future occasion when you will visit him.

3. "I am visiting my uncle tomorrow." - This sentence uses the present continuous tense. It implies that you have already arranged or scheduled to visit your uncle tomorrow.

So, while all three sentences convey the idea of visiting your uncle tomorrow, they slightly differ in terms of the focus on future intention (sentence 1), regular occurrence (sentence 2), and a scheduled arrangement (sentence 3).