Is there uniformity among words taking certain cases? Would "leżę na kobietie" be correct here and would the 'ie' ending be applicable to all female singular nouns taking the locative case?
In short 'lay' = 'to put something down'. If something is lying by itself you use 'lie'.
I'm a native English speaker and its "lying" not "laying". As #tadjanow says, "lay" is what you do to something (or someone!) else.
There is a usage "lay yourself down" but it needs the reflexive pronoun (or whatever its called in English, don't ask me! lol), and its the action of going INTO that position, not being in that position.
Colloquially in some parts of the English speaking world you can use lay = lie (cf. Bob Dylan, "Lay Lady Lay") but its not middle English.
At school our textbook used the term middle English to describe a form of standard English that could be used and understood anywhere throughout the modern English-speaking world.
This is totally different from the term Middle English (captial "M").
I did a google search for "middle English" and couln't find any instances of the old meaning I was taught. Maybe it's a term that is fallen out of use? Anyway, I will stop using it because it's so easily confused with "Middle English".
Maybe a better term for me to express the concept I wanted to express above is: "Standard written English".
Lay is also past tense of lie. "I lay down and fell asleep" vs "I lie down and fall asleep"
Can you accept "I am lying down on the sofa" as a correct answer.
When you say "lie down", people know you are talking about rest, not about making intentionally false statements.
Well, I thought it's only used for 'changing your position from vertical to horizontal', but apparently I was wrong and it can work here. Added now.
I lie upon the sofa- so I am wrong for using 'upon' instead of on. Oh dear...
Isn't it a bit bookish nowadays, though? Neither in this nor the apple sentence no one apart from you has reported it.
Lay is often confused with lie in English. Lie is correct in this case always.