-er
ər
-er is the hand that took the job
The picture Someone steps in front of an action and takes it into their hand — and that someone can be a machine. -er is whoever or whatever does that action; -ist is a person who learned a field and stands in it.
Where the picture shows up in -er
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the one who took the driving
The driver is waiting outside.
ðə ˈdraɪvər ɪz ˈweɪtɪŋ aʊtˈsaɪd
Your driver is waiting outside.
A person stands by the car door with a hand already reaching toward the wheel.
drive + -er.
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the machine that took the printing
The printer is out of paper.
ðə ˈprɪntər ɪz aʊt ʌv ˈpeɪpər
There's no paper in the printer.
A machine beside the desk pulls paper in, stamps letters on it, and pushes it out.
print + -er. The taker may be a machine.
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the one who took the cleaning
Ask the cleaner where the mop is.
æsk ðə ˈkliːnər wer ðə mɑːp ɪz
Ask the cleaning lady where the mop is.
At the end of the corridor, a person holds a mop and has the whole floor in hand.
clean + -er.
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the tool that took the opening
Do you have a can opener?
duː juː hæv ə kæn ˈoʊpənər
Have you got a tin opener?
A small piece of metal hooks its tooth on a tin lid and turns it open.
open + -er.
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the one who took the work
She is the best worker on the night shift.
ʃiː ɪz ðə best ˈwɜːrkər ɑːn ðə naɪt ʃɪft
She's the best on the night shift.
On the night floor, one person has a whole share of the work in hand and keeps moving.
work + -er.
All of it in one picture
-er is one hand that took a job. Take driving and you are a driver; take printing and you are a printer. Take cleaning and you are a cleaner, take the opening and you are an opener, take the work itself and you are a worker. It makes no difference whether the taker is a person or a machine. So when you see -er, just ask who or what took this job on.