The Vowels of Accented Syllables
§ 10. The Indo-Germanic vowel system was as follows:—
Short a, e, i, o, u, ə (1).
Long ā, ē, ī, ō, ū.
Note 1.—The sound of ə is not certain, but it may be taken as approximately that of the e in N.E. bitter. In Indg. it occurred in unaccented syllables only. In Germ, its history varied according to whether the syllable remained unaccented or took the accent.
Note 2.—Liquids and Nasals playing the part of vowels are written etc., in order to distinguish them from those used as consonants (§ 7, c).