REVISE
In unit 1, you learnt to use the articles: a/an.
Remember:
► In English we use A/AN before jobs: I am a teacher (NOT I am teacher)
► a- There are many professions ending in -ER; this changes the action to the person.
Example:
PAINT ⇒ PAINTER (the person who paints)
TEACHER ⇒ TEACHER (the person who teaches)
b- There are also some professions ending in -OR: DOCTOR, ACTOR
c- And others end in -MAN / -WOMAN: POLICEWOMAN, CAMERAMAN