1. All language of which grammar takes cognizance consists of sentences. The simplest complete sentence expresses the combination of a subject—that about which we speak (or think); and a predicate—that which we say (or think) about the subject. On the sentences which are (apparently or really) without a subject, see §§ 161 and 163.
2. In Greek (and generally in languages whose structure resembles that of Greek) every verb is a complete sentence, consisting of two parts, the stem, which expresses the predicate, and the ending, which expresses the subject. Thus ἔσ-τι he (or it) is, φα-θί say you, ἤλθο-μεν we came, are sentences; the several predicates are expressed by the stems ἐσ-, φα-, ἠλθο-, and the subjects by the endings -τι, -θι, -μεν. As the endings of a verb may always be translated by personal pronouns they are called the personal endings.
It may happen that the ending has been lost by phonetic corruption, as in ἔλαβε (for ἐλαβε-τ) he took. This however does not form a real exception, because in Greek such words are used exactly as if the lost ending were still sounded. In English it is different: took can only be used to express a predicate. The original subject is lost to the mind as well as to the ear.
It should be noticed that the term "verb" is used in grammars with a double meaning, sometimes of a single form—as when we say that ἐτύπτο-μεν is "a verb"—sometimes collectively, as when we say that ἐτύπτο-μεν is a "part" of "the verb" τύπτω. Here "a verb" means a group of forms, derived from a common root.