1. He is absorbed in biology.

2. He is very interested in biology.
3. He is into biology.
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Are they all the same in meaning?

Yes, they mean the same thing, but 3 is very, very casual -- slang!

1 is rather stuffy; 2 is the most common expression.

Yes, all three sentences have a similar meaning related to the person's interest and engagement in biology. Let's break down each sentence:

1. "He is absorbed in biology": This sentence implies that the person is deeply engrossed and fully focused on biology. They may spend a significant amount of time studying and exploring various concepts within the field.

2. "He is very interested in biology": This sentence indicates that the person has a strong attraction or curiosity towards biology. They may have a genuine passion for the subject and actively seek out opportunities to learn more about it.

3. "He is into biology": This sentence suggests that the person has a keen enthusiasm or interest in biology. The word "into" implies a sense of involvement, enjoyment, and possibly even a hobby-like dedication to the subject.

While all three sentences convey the person's interest in biology, they slightly differ in the intensity and focus of that interest.