If not, it is not a verb, but a participle. (Example: …have watched…watched is a ‘past participle’)

What’s wrong with the following utterances (sentences people said – the * denotes a truly wrong form):

1. *They might went
2. *We could wrote
3. …*to said..

Let’s look at some examples

We	went	shopping in the afternoon.
They	played	cards last night.
I	moved	last year.
She	taught	English (before she retired).
He	saw	nothing
We	looked at	each other.
The dog	barked	at the delivery van.
I	walked	my dog this morning.
They	biked	to work all year long.
We	hiked	in Italy this summer.

If you wanted to express that none of the things stated above happened…..

We	didn’t	go	shopping in the afternoon.
They	didn’t	play	cards last night.
I	didn’t	move	last year.
She	didn’t	teach	English (before she retired).
He	didn’t	see	anything (note the change of ‘nothing’ to ‘anything’).
We	didn’t	look at	each other.
The dog	didn’t	bark	at the delivery van.
I	didn’t	walk	my dog this morning.
They	didn’t	bike	to work all year long.
We	didn’t	hike	in Italy this summer.

The function of the English auxiliary is very important to understand. Whenever there is an auxiliary in a verb phrase: a form of BE or HAVE, may, might, should, could, must, will or would, the main verb – the verb that carries the meaning of e.g. an activity – is in the INFINITIVE form or a PARTICPLE. There are NO exceptions. It is ALWAYS like that. To understand DO or DID as auxiliaries you need to accept this fact of the English verb structure.

And after an infinitive TO (not TO the preposition), the verb is ALWAYS in infinitive form. So …to say and not …to said.

When we have a sentence in the simple past, that is all there is in the verb phrase: one verb in the simple past (see first group of examples). Nothing else.

Forming questions follows the same principle as stating something DID NOT happen. Using the examples above, form some questions.

Example: What did you do yesterday? When did you go shopping?

Note that, again, you have DID and an infinitive.

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