9. Verb Stem and Tense Stem. A comparison of the different forms of a Greek verb usually enables us to see that some one syllable or group of syllables is present in them all, as τυπ- in the forms of τύπτω, or βουλευ- in those of βουλεύω. This we shall call the verb stem. Α verb stem not derived from more primitive elements is called a root.
Again, the different forms belonging to any one tense are based upon a common part, which we shall call the tense stem. This part may be the same as the verb stem; or it may contain an additional element, as δι- in δί-δο-μεν, δι-δο-ίη-ν, etc.; -τε, -το in τύπ-τε-τε, τύπ-το-μεν, ἔ-τυπ-το-ν, τύπ-το-ι-μι, etc.
The subjunctive and optative, again, are distinguished by a suffix to the tense stem: e. g. δο-ίη-ν, διδο-ίη-ν, τύπτο-ι-μι, στήσα-ι-μι. The new stems so formed may be called mood stems.
Finally, the stems used in the historical tenses—the imperfect, aorist, and pluperfect—are formed from the tense stem by prefixing the augment.
The stems of the augmented forms are therefore parallel to the mood stems, the only difference being that they are formed by a prefix, while the mood stems are formed by a suffix. They may be described as time-moods of the several tenses—combining the notion of past time, which is expressed by the augment, with the meaning contained in the tense stem.
Each tense stem furnishes an infinitive and a participle. Thus we have (supplying one or two links by analogy) from the three tense stems βαλλε (or -ο), βαλε (or -ο), βεβληκα.
It is evident that there might have been a future time-mood as well as a past for each tense stem. In English indeed we can distinguish progressive action in the future as well as in the present and past: I shall be writing as well as I am writing and I was writing. See Goodwinʼs Moods and Tenses, § 65; Driver's Use of the Tenses in Hebrew, § 4. Modern Greek has two such futures, θὰ γράφω I will be writing and θὰ γράψω Ι will write, related to each other as ἔγραφον and ἔγραψα.
10. Formation of Tense Stems. Leaving out of sight the meanings of the several tenses, and looking to the mode of their formation, we may distinguish the following groups
- With the verb stem serving as tense stem
The simple athematic present, as φημί.
The simple athematic aorist, as ἔ-βη-ν.
The aorist in -ᾰ, as ἔ-χευ-α.
- With tense stem enlarged from verb stem
The athematic reduplicated present, as τί-θη-μι.
The present in -νη-μι and -νῡ-μι, as σκίδ-νη-μι, δείκ-νῡ-μι.
- With the thematic vowel
The ordinary thematic present, as λέγω.
The present with short stem, as ἄγω.
The simple thematic aorist, as ἔ-λᾰβ-ον.
- With reduplication (thematic)
The thematic reduplicated present, as γί-γν-ο-μαι.
The thematic reduplicated aorist, as ἤγ-ᾰγ-ο-ν.
- With other suffixes (athematic)
The aorist in -σᾰ, and in -σε, -σο.
The aorist in -η-ν (2nd aorist passive).
The aorist in -θη-ν (1st aorist passive).
- With other suffixes (thematic)
The present in -τω (τ-class of Curtius).
The present in -νω (Nasal Class).
The present in -σκω, and the iterative forms.
The present in -ι̯ω (ι-Class).
The future in -σω, -(σ)ω.