An infinitive in Greek can be adverbial, adjectival, or substantival. Study BBG chapter 32 or this video. The infinitive is identified by its own unique set of endings:
λυω |
present |
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λυειν |
λυσαι |
λαβειν |
λελυκεναι |
|
λυεσθαι |
λυσασθαι |
λαβεσθαι |
λελυσθαι |
|
λυεσθαι |
λυθηναι |
γραφηναι |
λελυσθαι |