IRREGULAR PLURAL FORM

There are tens of words that differ from singular to plural.
Take a look at a short list of them:

CHILD - CHILDREN
MAN - MEN
PERSON - PEOPLE
FOOT - FEET

The ones above are constantly drilled by teachers, right?
What about the following ones?

STAFF - STAFF
BACTERIUM - BACTERIA
DEER - DEER
AIRCRAFT - AIRCRAFT
APPENDIX - APPENDICES
BOOTH - BOOTHS

Attention to verb conjugation when using the words above:

The staff were really helpful.
The bacteria have spread to other parts of the body.
Both booths are broken.


Best wishes,
André