The's no single word that you can use to replace is. It depends on the context.
Examples
The book is lying on the table (for The book is on the table).
The castle stands at the top of the mountain (for The castle is at the top of the mountain).
Instead of using the word challenging you can use the word gifted, special, special gifted.
or
Will, when, why, it, can
I have a stomach ache.
Myself
mixture
are
Another word you can use instead of obituary is "death notice" or "memoriam."
Use the word "how" when asking "in what manner". Use the word "why" when asking "for what reason".
use the word job
used to be
is, it, in the past.