It depends on the situation and plurality, but generally: שמח (Sah-may-ach).
There is no such thing as "Hebrew Orthodox". There is only Hebrew. In Hebrew, you usually do not mention the name of the holiday in greetings. So you would just say Happy Holiday, which is hahg same'akh (חג שמח) Some communities do say Hanukkah Same'akh (חנוּכה שמח) meaning "Happy Hanukkah".
If you are asking how to say "Happy New Year" in Hebrew, it's shanah tovah (×©× ×” טובה)
You can't say Happy Friday in Hebrew, but a common greeting on Friday afternoons is Shabbat Shalom (שבת שלום).
This is how you say Happy Earth Day in Heberw, I just do not know how you say it i know how to write it and read it. :)(:
Chag sameach, chaverim!
You can say Khag Purim Same'akh (חג פורים שמח) but it's more common just to say Khag Sameakh, which means happy holiday.
Me'od same'ach (מאוד שמח) Me'ushar (מאושר)
You would just say Chag Sameach (חג שמח)
There's no real way to say that in Hebrew. If you mean "be happy" then it's: to a male: תשמח (tees-MAHKH) to a female: תשמחי (tees-meh-KHEE)
"Happy Pesach!" Some people will say 'happy Pesach'. However, most people will use the Hebrew 'Chag sameach' (happy holiday) or 'Chag Pesach sameach'.
In Hebrew you say "chag Sameach"*In English you say "Happy Passover"Unless your friend is over the age of 80, it's unlikely he'd be familiar with the Yiddish greeting. But if that's the case, you can say “A koshern un freilichen Pesach”* (pronounced: A KUH-sher-in OON FRAY-lech-in PAY-sach).*The ch is a guttural sound.
Yom bossim same'ach (יום בוסים שמח)