I came across the following sentence:
我既是一个语言的从教者，也是一个语言学习的爱好者。
I understand that "既 A , 也 B" is a sentence structure for expressing "both .. and ..".
I was wondering about what effect 既 has on the meaning? Consider the same sentence above with 既 omitted:
我是一个语言的从教者，也是一个语言学习的爱好者。
Has the meaning or feeling of the sentence changed? Is either preferred in some contexts?
我是一个语言的从教者，也是一个语言学习的爱好者。
This sentence reminds us of the fact that I'm also a language hobbyist(assuming I'm well known as a 语言的从教者).
我既是一个语言的从教者，也是一个语言学习的爱好者。
With 既, it parallels the two roles (语言的从教者 and 语言学习的爱好者), which share the same level of importance.
Quote:- "Has the meaning or feeling of the sentence changed? Is either preferred in some contexts?"
(1) the meaning has not changed.
(2) the "feeling" may have shifted, if by feeling you mean the thought-processes you wish to convey to or impress upon the listener. The 既是，也是 is to convey to the listener the "contra-duality" of a certain personal circumstance, predicament or function that's significant to you.
Without the 既是, the impact of the contra-duality point you are trying to make is less effective, because it serves to alert the listener that something of significance is about to follow.
