1. The formation of the parts of speech from the stems (derivation), and their inflexion, are effected in two ways:
(a) internally by changes in the stem itself, particularly in its vowels:
(b) externally by the addition of formative syllables before or after it. The expression of grammatical relations (e.g. the comparative degree and some case-relations in Hebrew) periphrastically by means of separate words belongs, not to etymology, but to syntax.
The external method (b) of formation, by affixing formative syllables, which occurs e.g. in Egyptian, appears on the whole to be the more ancient. Yet other families of language, and particularly the Semitic, at a very early period had recourse also to the internal method, and during their youthful vigour widely developed their power of forming derivatives. But the continuous decay of this power in the later periods of language made syntactical circumlocution more and more necessary. The same process may be seen also e.g. in Greek (including modern Greek), and in Latin with its Romance offshoots.
2. Both methods of formation exist together in Hebrew. The internal mode of formation by means of vowel changes is tolerably extensive (קָטַל, קָטֵל, קָטֹל; קִטֵּל, קֻטַּל, &c.). This is accompanied in numerous cases by external formation also (הִתְקַטֵּל, הִקְטִיל, נִקְטַל, &c.), and even these formative additions again are subject to internal change, e.g. הָתְקַטַּל, הָקְטַל. The addition of formative syllables occurs, as in almost all languages, chiefly in the formation of the persons of the verb, where the meaning of the affixed syllables is for the most part still perfectly clear. It is also employed to distinguish gender and number in the verb and noun. Of case-endings, on the contrary, only scanty traces remain in Hebrew