Did you know that beginning in Greco-Roman times, the Greek infinitive began to decline in popular usage, and by the Byzantine period had all but disappeared in common communication? There are a lot of little linguistic jewels in this description by Antonius Jannaris in his Historical Greek Grammar:
Notwithstanding its convenience, the Greek infinitive, compared with its two associates — noun and finite verb — from the outset labored under several serious disadvantages. In the first place, as a noun, it lacked nominal inflection, having neither case-endings nor plural form, and thus appeared abnormal and foreign to the genius of the Greek language which at no time admitted of a noun without inflectional properties. Then as a verb, it was still more indefinite, since it indicated neither number nor person, often also no precise time. Now when it is remembered that the cardinal points aimed at in popular discourse are simplicity, perspicuity, and emphasis, and that, speaking of the Greek language in particular, these conditions have at all times been fulfilled by means of inflectional properties (endings, prefixes, etc.), it is evident that the absense of these requisites from the infinitive often rendered it unfit for the purpose. As a natural consequence, popular discourse began as early as Greco-Roman times to dispense with the infinitive and replace it either by equivalent abstract nouns (in –ma, –ion, –mos, –sis, –sia) or finite moods (hina with primary subjunctive, hoti with indicative). This process of retreat and substitution, though slow in its manifestation, advanced steadily and reached its close in early Byzantine times. All subsequent cases of the infinitive, whether nominal or verbal, savour of scholasticism or literary mannerism.*
If you’re a suffering first-year Greek student, a wide-eyed second-year amateur, a third-year Greek geek, or a bonafide tutor or teacher, keep going. There’s always more to learn, and when you turn to the New Testament, the windows will be blown open.
* Antonius N. Jannarus, An Historical Greek Grammar Chiefly of the Attic Dialect (Hildesheim: G. Olms, 1987), p. 480, §2063.