https://www.chabad.org/holidays/passover/pesach_cdo/aid/3584633/jewish/How-to-Wish-Happy-Passover.htm#:~:text=But%20what%20to%20say%3F,sah-MAY-ach).
The traditional Ashkenazic greeting is “gut yom tov” (with “u” as in “put”). “Yom tov,” which literally means “good day” in Hebrew, denotes a holiday. In Yiddish, it is normally mangled into something that sounds more like “YON-tiff.” Thus, the greeting can sound like “gut YON-tiff” or even “gutJONtiff.” (Translated into English, the “gut yom tov” greeting is strangely redundant, meaning “good good day.”)
Sephardic Jews prefer the biblical term for a festival, “chag.” Thus, when wishing someone a joyous festival, they say “chag same’ach” (pronounced CHAG sah-MAY-ach). This greeting has its roots in the Torah, where forms of these two words are used in the commandment to rejoice on the festivals.1
Now, not all holidays are considered equal. The intermediate festival days of lesser sanctity, when many of the work restrictions are relaxed, are called Chol Hamoed. On those days, the traditional Ashkenazic greeting is “gut mo’ed” (or “gut MOY-ed”), and Sephardim say “mo’adim l’simchah,” to which some respond “chagim u’zemanim l’sason.” (As before, the Sephardic salutation has liturgical roots; these phrases are lifted straight from the holiday kiddush.)
If you want to greet someone, but are not sure what to say, just let the other person greet you first, and then repeat the greeting. Works every time.
Lastly, have you ever wondered what to wish people after Passover has ended? The traditional Yiddish Post-Passover greeting is for “a gezuntn zumer,” a healthy summer.