Shecheyanu is the shorthand for one of the best known Jewish blessings, shehecheyanu vkiyimanu vhigayanu lazmam hazeh, who has kept us alive and sustained us and enabled us to reach this moment.
Shecheyanu is a blessing of thanks and appreciation that is said when we do or experience something new, or renewed, that is something we have not experienced in a long time. We say shecheyanu when we first put on new clothes, enter a new house, use new utensils or furniture, eat a new fruit for the first time in the season , celebrate a Jewish holiday, fulfil an unusual mitzvah, or see a friend whom we have not seen in more than 30 days.
It is also possible to say shecheyanu on other exceptional moments. Rabbi Yehuda Leib Maimon said it at the Declaration of the State of Israel on May 14 1948.
Shecheyanu is a transitive verb built from the word chai, meaning life. The word therefore means who has kept us in life.
The popularlity of shecheyanu, even among Jews who do not usually say blessings, may be because it is expresses a universally recognisable gratitude and appreciation for being alive and for the power to use life for worthwhile ends.