Other forms: laid, laying, lays
To lay is to put something down flat and carefully. Lay the table, lay a carpet, lay the baby in the cot. It is irregular: lay, laid, laid.
This is the verb English speakers argue about, and the rule is simple even if the practice is not. Lay takes an object — you lay something down. Lie does not — you lie down yourself. The confusion comes from the past tense of lie, which is lay: I lie down today, I lay down yesterday. So lay is both the present of one verb and the past of the other, and there is no way round learning both tables. Hens lay eggs, which is the same verb doing exactly what it says.
1verblayTo put something down carefully.
“She laid the letter on the table and stepped back.”
2verbarrangeTo arrange or install something over a surface.
“They laid the new floor in a day.”
3verbbirdOf a bird, to produce an egg.
“The hens have stopped laying.”
4verbsetTo set out plates and cutlery for a meal.
“Lay the table, we are eating in ten minutes.”
Too few real examples of this word to estimate which sense is commonest.
lay is a way of putting down.
Old English lecgan was the causative of licgan, to lie — it meant to cause something to lie. That is precisely the modern rule: lie is what a thing does, lay is what you make it do, and the two have been tangled since Middle English.
Proto-Indo-European
*legʰ-
Proto-Germanic
*lagjaną — to lay
Proto-West Germanic
*laggjan
Old English
leċġan — to lay
Middle English
leyen
English, today
lay
Middle English leyen, leggen, from Old English leċġan (“to lay”), from Proto-West Germanic laggjan, from Proto-Germanic lagjaną (“to lay”), causative form of Proto-Germanic ligjaną (“to lie, recline”), from Proto-Indo-European legʰ- (“to lie, recline”). Cognate with stq lääse (“to lay; to lie”), West Frisian lizze (“to lay, to lie”), cim leng (“to lay”), Dutch leggen (“to lay”), German legen (“to lay”), li lègke (“to lay”), lb leeën (“to lay”), Yiddish לייגן (“to lay”), Danish lægge (“to lay”), Faroese -, Icelandic leggja (“to lay”), Norwegian Bokmål legge (“to lay”), Norwegian Nynorsk legga, legge, leggja, leggje (“to lay”), Swedish lägga (“to lay”), Gothic 𐌻𐌰𐌲𐌾𐌰𐌽 (“to lay”), Old French laier, laiier, laire (“to leave”), Albanian lag (“troop, band, war encampment”).
Etymology from Wiktionary, CC BY-SA