Learn English – A single word for “the space in between”

Is there a single word that can be used instead of "the space in between"? I am looking for something general.

Few words I thought of are period, interspace, mezzanine.

For example:

The space in between fear and love is filled with uncertainty.

The space in between birth and death is life.

The space in between knowing and believing is something.

I like the word mezzanine but I am not sure if it fits since by definition it relates to architecture. Interspace, on the other hand, sounds like something related to science fiction. Period is about time.

An example of how I would like to use it:

[Word] of fear and love is filled with uncertainty.
[The mezzanine] of fear and love is filled with uncertainty.
[The interspace] of fear and love is filled with uncertainty.