When to use “as” or “as a”

Question

I saw the same question but it's always regarding professions like:

a) As teacher, I meet many children.

b) As a teacher, I meet many children.

In this case I would automatically say b) because it's what sounds better and is in fact the correct answer, for what I've gathered.

But my question is not profession related and I've seen it written in both ways:

a) We can use my body/floor/wall as canvas.

b) We can use my body/floor/wall as a canvas.

I feel like the first one sounds better but maybe I have it all wrong, perhaps because in my mother language we can say it both ways and we don't have to use "a" because the translation would be something more related to "one", and in this case i'm talking about the canvas more in an abstract way. I don't know if this makes any sense.

Answer 1

The answers so far ignore the way that "as" can be followed by a post or role without an article: as president, as secretary, as mediator, as champion, as referee, as recipient.

Teacher is usually seen as a profession, rather than a post or a role, so as a teacher is more likely. But it could be a specific role: consider as head teacher, or as teacher to the Royal family.

Answer 2

'Teacher' is a singular countable noun, which almost always needs 'a' (or a similar word). 'Canvas' can be uncountable (Many painters paint on canvas), or singular countable (I need to buy a canvas for my next painting). Saying 'use ... as canvas' means 'as canvas in an uncountable way'. Most of the time you would use your body, or one floor or one wall as 'a canvas' for one painting. Maybe actual painters say 'use ... as canvas' but it sounds very strange to me.

Answer 3

The easy part of the answer is that you use a with countable nouns (in this context, at least), and use no article with uncountable nouns.

The tricky part is that a lot of nouns have multiple definitions, and those can differ in terms of whether the noun is countable or uncountable. "Canvas" is one of them. When used as an uncountable noun it refers to the material in general, and when used as a countable noun it refers to a specific piece of that material.

In your case, I'd say both "as canvas" and "as a canvas" are correct - you can use your body as the material to paint on, or as a specific piece of that material you're going to paint on, and the distinction is largely meaningless.