Representative Paradigms: Infinitive
Here’s an basic thematic verb that is sigmatic in the aorist:
PROGRESSIVE
| ACTIVE λύ/ειν > λύειν | MIDDLE λύ/εσθαι > λύεσθαι | PASSIVE ⬅︎ same as middle |
FUTURE
| ACTIVE λύ/σ/ειν > λύσειν | MIDDLE λύ/σ/εσθαι > λύσεσθαι | PASSIVE λυ/θήσ/εσθαι > λυθήσεσθαι |
AORIST
| ACTIVE λύ/σ/αι > λύσαι | MIDDLE λύ/σ/ασθαι > λύσασθαι | PASSIVE λυ/θή/ναι > λυθῆναι |
PERFECT
| ACTIVE λε/λυ/κ/έναι > λελυκέναι | MIDDLE λε/λύ/σθαι > λελύσθαι | PASSIVE ⬅︎ same as middle |
For contract verbs like τιμα/, καλε/, and δηλο/, see here. Only the progressive active infinitive of these verbs is noteworthy.
Here’s a basic thematic verb that follows predictable rules of ablaut <link> and is asigmatic in the aorist:
PROGRESSIVE
| ACTIVE λίπ/ειν > λείπειν | MIDDLE λίπ/εσθαι > λείπεσθαι | PASSIVE ⬅︎ same as middle |
FUTURE
| ACTIVE λίπ/σ/ειν > λείψειν | MIDDLE λίπ/σ/εσθαι > λείψεσθαι | PASSIVE λιπ/θήσ/εσθαι > λειφθήσεσθαι |
AORIST
| ACTIVE λιπ/εῖν > λιπεῖν | MIDDLE λιπ/έσθαι > λιπέσθαι | PASSIVE λιπ/θή/ναι > λειφθῆναι |
PERFECT
| ACTIVE λε/λιπ/έναι > λελοιπέναι | MIDDLE λε/λίπ/σθαι > λελεῖφθαι* | PASSIVE ⬅︎ same as middle |
* When a marker that begins with /σθ- is added to a stop consonant, as here, the σ drops. If the result is a double dental, σ is inserted and the first dental drops according to the Double Dental Rule <link>. For instance: πε/πίθ/σθαι > πεπεῖθθαι > πεπεῖθσθαι > πεπεῖσθαι.
And here’s a standard athematic /μι verb:
PROGRESSIVE
| ACTIVE δι/δό/ναι > διδόναι | MIDDLE δί/δο/σθαι > δίδοσθαι | PASSIVE ⬅︎ same as middle |
FUTURE
| ACTIVE δό/σ/ειν > δώσειν | MIDDLE δό/σ/εσθαι > δώσεσθαι | PASSIVE δο/θήσ/εσθαι > δοθήσεσθαι* |
* It is usually the case that a short vowel lengthens when an aspect marker is added to it. So why not δωθήσεσθαι? Well, a 9th century CE Byzantine law book called the Prochiron has the 3rd person singular future indicative passive form δωθήσεται (2.4.7) instead of δοθήσεται. So presumably someone somewhere said δωθήσεσθαι instead of the standard δοθήσεσθαι.
AORIST
| ACTIVE δο/έναι > δοῦναι | MIDDLE δό/σθαι > δόσθαι | PASSIVE δο/θή/ναι > δοθήναι |
PERFECT
| ACTIVE δε/δο/κ/έναι > δεδωκέναι | MIDDLE δε/δό/σθαι > δεδόσθαι | PASSIVE ⬅︎ same as middle |
Another way to think about the morphology of infinitives is by formation. See here for more.
reading morphologically 