In Masechet Horiot page 10 Rabbi Yehoshua says that there is a star that appears once every 70 years. It is clarified in another source that this star is really a comet, so why does the Talmud call it a star?
The word ‘star’ in the Gemara refers to any light in the night sky. See the verse: “Praise Him, sun and moon, praise Him, all the stars of light” (Tehillim/Psalms 148, verse 3). The Gemara may sometimes call a falling star a ‘comet’ but not necessarily. It is important to note that our modern Hebrew is not the same Aramaic-Hebrew of old, therefore, some expressions may vary.