Χαίρετε!
Dr. Mastronarde’s Introduction to Attic Greek in Chapter 24 says that the aorist of ἵστημι has a transitive and intransitive form. What about the present and future? If I wanted to write, “I am standing up” or “I will be standing up,” do I use a middle/passive form of ἵστημι or do I use some other word?