You are laying something — the verb needs an object: <em>She was laying the tiles when the rain started.</em> You are lying if nothing is being put anywhere: <em>The dog was lying in the doorway.</em> Lying also covers telling untruths: <em>He knew she was lying about the receipt.</em>
The core difference
Lay is a transitive verb: something has to receive the action. You lay a book on the table, lay a carpet, lay an egg. Lie is intransitive — the subject simply is somewhere, and nothing is being placed. You lie on the sofa, lie awake, lie in wait.
The -ing forms inherit that split exactly. Laying nearly always has an object nearby; lying never does.
How to use each
- Laying (putting something down): He's laying new floorboards in the hall. / They're laying the table for eight. / The hens have stopped laying.
- Lying (reclining, being situated): I've been lying here since six. / The village lies in a valley, so "the village is lying" would be odd — use plain lies.
- Lying (not telling the truth): She's lying to protect her brother.
The test
Ask: laying what? If you can answer — the baby, the bricks, the blame — write laying. If there is no answer, write lying. Another version: if you could swap in placing or putting, it's laying; if you could swap in resting, it's lying.
One group of exceptions is worth knowing: a few established uses of lay drop the object and still take the a — hens that have stopped laying, laying off staff, laying into someone. Learn those as set phrases; everywhere else, no object means lying.
So I'm going to lie down is right, because you can't say "I'm going to place down." And I'm laying down the rules is right, because the rules are the thing being put down.
Why so many people get it wrong
The confusion is not carelessness — it is built into the language. The past tense of lie is lay. So Yesterday I lay in bed all morning is correct, and it looks exactly like the other verb. Once lay is doing double duty, the present tense gets contaminated, and I was laying in bed starts to sound normal. It is very common in speech, and no reader will misunderstand you — but it is still marked as an error in edited writing.
The full sets are worth memorising: lie, lay, lain, lying (rest); lay, laid, laid, laying (place); lie, lied, lied, lying (tell untruths).
The edge case
Watch for objects that don't look like objects. Laying claim to the estate and laying siege to the city both take objects (claim, siege), so laying is correct. Conversely, the responsibility lies with the board has no object at all — lies, never lays.
Frequently Asked Questions
Is it "laying in bed" or "lying in bed"?
Lying in bed. Nothing is being put anywhere, so the intransitive verb is the right one. "Laying in bed" would only work if you finished the sentence with an object, as in laying tiles in bed, which nobody does.
Is it "laying down" or "lying down"?
Both exist but mean different things. You lie down to rest; you lay something down — a weapon, a rule, a deposit. "I need to lie down" is the one you almost always want.
What about the past tense — "I lay down" or "I laid down"?
If you rested, it's "I lay down for an hour." If you put something somewhere, it's "I laid the parcel on the step." The lookalike past tense of lie is the main reason this pair goes wrong.