😦 Several audiences left before the film finished.
Audience is indeed countable but it is a ‘collective’ noun, and so an (=1) audience can comprise many people. If you want to focus on a subgroup of an audience then it is common to refer to these people as ‘members of an audience’:
🙂 Several members of the audience left before the film finished.
An example of audiences (plural) might be:
🙂 The opening of the new James Bond film was enjoyed by audiences up and down the country.
In this case the same film was watched simultaneously by many different groups of people (audiences) in many different locations.
I’ll end this post with two illustrations. The first shows audience, the second audiences.
😦 I am a staff at the Ministry of Religious Affairs.
Although you will occasionally find an example of staff as a countable noun, it is extremely rare.
Used as an uncountable noun, staff refers to people who work for a particular organisation:
🙂 Staff at the Ministry of Religious Affairs receive a competitive salary.
Used as a countable noun, a staff is a kind of stick with certain features and functions:
- often very long – longer than its user is tall
- usually made of wood
- usually quite ornate, possibly hand-crafted
- used by someone with special powers, for example a wizard
- often used in specialised fighting, like kung fu
- otherwise used to assist in walking (elderly people, etc)
🙂 He used his staff to scare away evil spirits and then used it to turn my horse into a brand new Ferrari. I noticed the staff also helped him to walk!
In the context of your writing one of these meanings, staff countable / staff uncountable, will probably be more obvious than the other. However, if you want a high score in IELTS for vocabulary, I suggest you choose the most appropriate meaning!
If you really must use a countable noun, you can do this:
🙂 I am a member of staff at the Ministry of Religious Affairs.