What is a one-word noun that represents "an empty thing"? I looked at synonyms of "empty" but they seem to be all adjectives. I need a noun.
The intended usage is to describe a piece of cake which has no toppings on it. I could say "empty piece", but I am looking for a single-word noun. The closest words that I found so far are "hole" or "hollow", but they do not exactly match the intended meaning.
You've edited the question to be specific to cake:
A plain cake is a cake without any toppings.
A blank cake as suggested in the comments is one which is topped and ready for a message to be written on it.
In the UK, I've never heard 'blank' used for pieces of cake, only for whole cakes - if you were going to write on it, then you wouldn't already have cut it up. If you really wanted to say 'here is a an iced piece of cake for you to write a message on', then you might say 'blank piece of cake'; for every other use it would be 'piece of plain cake' if not topped or 'piece of cake'.
'Void' seems to be my understanding of your word. It can be used both as an adjective and as a noun. Could you elaborate more on the context in which you are looking to use the word?
noun
1. a space entirely devoid of matter.
synonyms: empty space, emptiness, void, nothingness, vacuity, vacancy; rarevoidness, nihility "the experiment has to be conducted in a vacuum"
'Null' is a common synonym for 'empty'.
In fact, in mathematics, these are both used to describe the set with no elements.
'Null and void' (Note: I got 'void' from Ankit's answer) is actually a very common idiom, meaning: without legal force or effect; not valid. Source: Dictionary.com
e.g. This contract is null and void.
Note however, that null and void are actually both synonyms of each other (and empty).
Apart from that, looking up the synonyms of 'void' will generate a lot of viable alternatives.
If you know what the "thing" is and it's a container, then empty X is the usual way to express it. English doesn't have a general single word for empty container. If you really don't know what X is, and you don't care, then say anything/something that's empty or anything/something empty.
Spot refers to a place in a line, grid, or other physical arrangement. If nothing is in such a place, you can use spot to refer to that empty place.
The word 'cake' by itself does not connote the presence of frosting.
From Merriam-Webster:
cake:
1a : a breadlike food made from a dough or batter that is usually fried or baked in small flat shapes and is often unleavened
To your first question, shell or husk would be something that was empty, but is not useful in the example usage you asked for subsequently.
From Merriam-Webster:
shell:
4c : a casing without substance
mere effigies and shells of men — Thomas Carlyle
and
husk:
2b : an emptied shell
