The cAr is stationAry, a pEn is stationEry

[avenueq]

That's how to remember it.
Please.
Thank you

@LizzieSiddal

Just use spell check.

But the OP and most of this thread is about how to remember the different spellings of sets of homophones. The incorrect options are correctly spelled, just not the word the writer wants in a particular situation. Spell check is useless here (though it does help with diarrhoea, if you're on a device with the feature available)!

Incidentally, I was taught that "a cAR is stationARy, papER is stationERy."

NeCeSSary. One collar, two socks (from the shapes of the letters). Sesame Street tip, I think. Never forgotten it.

I've always used envelope to help me remember.

Spellcheck tends to use American spellings. To explain the difference between win and beat my old English teacher said “if I win you I will take you home and put you on the mantelpiece” I have never forgotten.

peek (two eyes peeking with the ee)
peAk (mountain top with the A)

Discrete - the Es are separated by the T.

Discreet - the Es are cuddled together so they can whisper secrets without being overheard.

OMG - yes! I was looking for some themed stationery yesterday on Amazon, and it actually had the gall to say:

‘showing results for stationARY - please click here if you wish to continue with your original search for stationERY’... which I did, and there were no results vs. hundreds with the other spelling

I had a complete wobble that my whole life had been a lie and googled the spelling to check. No, I was right, E for Envelope, stationERY!

I’m so glad I have found my people lol!

I'm another one who always remembers the E in Envelope.
I sell parts for stationary engines and still have to think every time before I write it down.