Which is the closest synonym for word currently?

The closest synonym for "currently" depends on the specific context. Here are some possibilities:

General usage:

* Now

* At present

* Presently

* Right now

* At this time

* In the present

* As of now

More formal usage:

* Contemporaneously

* Simultaneously

* At this juncture

The best synonym will depend on the specific sentence and the desired level of formality.