The reason you call it a building is because it was built as you would call something that was carved a carving or something that was painted a painting.
an invention
A blacksmith:)
Step 1: you call someone to do it for you
a nuclear engineer.....
The word specialty is a noun. It is something in which someone specializes.
you call them able?
you call them able?
a diamondologist which is a subset of gemologists (study all precious and semi-precious stones)
a souvenir
space is a bit of a broad speciality... Astronomer is the most broad I can think of, recommend me if that is right.
That is asault and you can call the police.
slut, whore
An immortal. Deathless.
...registration?
Imaginative
A specialist is one who specializes is something. A medical terminology combining form for a specialist is -ologist.