Learn English – Difference between “novel” and “fiction”

Skeptical means “having reservations”. Someone who is skeptical will not easily be convinced, will be hard to persuade.

The main meaning of cynical is “believing the worst of people”, or as NOAD says, “distrustful of human sincerity or integrity”. By extension, it has come to mean “doubting something will happen”, which can be somewhat close in meaning to skeptical in some cases, but not generally.

As an example, in the sentence “John is skeptical about the motorway extension”, you could replace skeptical with cynical without altering the meaning. In the sentence “John is skeptical about global warming”, you could not do this change. Likewise, in “John has a cynical attitude”, you could not use skeptical instead.

Firstly, a period or 'full stop' signals the end of a sentence, i.e., a complete statement or idea that is independent.

"I see. I see"

Two individual sentences. Two thoughts. That they are identical is merely incidental. Here it is either a simple repetition or, esp. in speech, depending on intonation, a very different pair of ideas conveyed.

"I see, I see"

One sentence. One thought. The second occurrence reinforces ("Have no doubt, I confirm."), modifies, (per intonation, cf. above) or restates differently to complete the expression.

The reasoning is more reflective in the second example.

"My house, my rules" vs. "My house. My rules"