What short word in Japanese means Hi! in English?

Hi, everyone!

Last week, I have sent an E-mail to my favorite podcast station,
aaaand, they read it! Wow!!
Now, I’m trying to send next one, but I have one thing I need to make sure.

I want to let them know a Japanese word used for greetings.
Because, when people in my favorite podcast get an E-mail from a country out of U.S.A., they say a very short word which may be used as a greeting in the mailer’s country.

What do you think is the best word for Japanese?

I came up with the word “まいどー”, you know, I’m from Kansai area, but I don’t think it’s a good idea.
I want to have a very short word which can be pronounced easily for Americans and is also used both men and women in Japan.
If you have any idea, please let me know.
Thanks.