how to i send an iMessage to an android phone?

You can't send iMessages to an Android phone. You can only send SMS messages. The Message app on your iPhone will automatically send any messages in the appropriate format - iMessage to iMessage users and SMS to everyone else. If you are unable to message someone with an Android phone, you'll need to contact your carrier as SMS is a carrier function.

iMessages can only be sent and received with Apple devices. SMS/MMS messages can be sent/received on any phone. When you sent a message from your iPhone to an Android phone, it is a SMS/MMS message, not an iMessage. See information in the following article: What is the difference between iMessage and SMS/MMS? - Apple Support

You can send messages to an Android phone from your Mac if you send it though your iPhone as described in Forward SMS/MMS text messages from your iPhone to your Mac or iPad - Apple Support

Note that they will be SMS/MMS not iMessages.

MarkSamuelTuttle wrote:

Thank you.

So, is it impossible to do this from my Mac laptop?

Can I tell laptop to translate to the correct format?

--Mark

Apologies for misunderstanding your original question. But, FoxFifth was on point.

If you follow the directions in the final link FoxFith provided, yes, you will be able to send SMS messages from your Mac to Android users.

Do you own an iPhone? That is a key part.