I'm beginner using Blender 2.91.0. I'm following tutorials and I tried to search "separate" but nothing shows up in obejcet mode.
+Thanks for answer and comments.
I was following this tutorial: youtube.com/watch?v=At9qW8ivJ4Q. I found out that separate is only possible in edit mode before asking this question. However on the video at at 1:00:54, it seems that Separate is possible in object mode. Mine still didn't work in object mode, so I was curious about it.