13. The endings of the active participle to indicate gender are respectively —ων, —ουσα, —ον. The form —ουσα is of the first declension; the others (—οντ, Gn. 25; Gl. 119) are of the third.
14. Middle participles are of the first and second declensions and may be recognized by the syllable —μεν—. E. g., λυ-ό-μεν-ος.
15. The active infinitive regularly ends in —ειν —εν + theme vowel —ε—, contracted, —ειν). E. g., λύ-ειν (for λυ-ε-εν). The passive and middle (i.e., when used as passive) infinitives regularly end in —σθαι. E. g., λύ-ε-σθαι, λύ-σ-α-σθαι. The aorist passive infinitive ends in —ναι. E. g., λυ-θῆ-ναι. Bt. 167; Gl. 162, 273, 275; Gn. 301, 334.
16. Variations from the regular forms occur in the endings of the imperative:
| Active | Middle and Passive | |||||
| Sing. |  | |||||
| 2. | —, aorist —ν (—θι, —ς) | —σο aorist —αι | ||||
| (contracts with con. vowels ιο —ον) | ||||||
| 3. | —τω | —σθω | ||||
| Dual | | |||||
| 2. | —τον | —σθον | ||||
| 3. | —των | —σθων | ||||
| Plur. | | |||||
| 2. | —τε | —σθε | ||||
| 3. | —ντων (or τωσαν) | —σθων (or —σθωσαν) | ||||
| Bt. 167; Gl. 270-2; Gn. 746; H.A. 376. | ||||||
17. The principal parts of the verb (which should be memorized) are the first person singular of the active indicative present, future, first aorist, and perfect; the middle perfect; and the passive aorist. Bt 162-3; Gl. 311; Gn. 462-5; H.A. 304c.
18. A small class of verbs (about equal to the number of irregular verbs in English) retain the more primitive personal endings (e.g., act. ind. pres. sing., —μι, —σι, —τι, remains of old pronominal forms). Of such are τί-θη-μι, δί-δω-μι, ἴ-στη-μι. Bt. 251-8; Gl. 372-4; Gn. 500-509; H.A. 476-92.
19. Certain verbs with vowel stems, as τιμά-ω, φιλέ-ω, δηλό-ω, by contraction with initial vowels in the personal endings assume forms not found in the regular verb paradigms. E. g., τιμά-εις, τίμᾶς; ἐ-τίμα-ε, ἐτίμα; ἐ-τίμα-ο-ν, ἐ-τίμων. Bt. 248-50; Gl. 313-15; Gn. 492-94; H.A. 337-41. For changes in accent see: Bt. 65; Gl. 29, Gn. 117; H.A. 37-39.
(1) These forms are best studied as they occur by reference to the grammars.