Is it spelled heil or hail?

Both heil and hail are correct spellings, but they are different words from different languages with different meanings and uses. Hail is the standard English word. As a noun, it means frozen rain pellets, as in a hail storm. As a verb and interjection, it means to greet, acclaim, or salute, as in hail a taxi or hail to the chief. It comes from Old Norse heill meaning health. Heil is a German word that means healthy, whole, safe, or intact, and as an interjection it means hail as in may you be healthy. The phrase heil Hitler is German for hail Hitler. In English texts, heil appears only when quoting German, particularly in historical contexts related to Nazi Germany and the phrases Sieg Heil and Heil Hitler used as a Nazi salute from 1933 to 1945. So if you are writing in English about weather or greeting someone, you spell it hail. If you are writing about German history or quoting German, you spell it heil. The confusion arises because they sound similar and have a common ancient Germanic root, but in modern English, hail is the correct English spelling for all normal uses, while heil is considered a German loanword used only in specific historical references and is offensive when used outside historical discussion due to its Nazi association.