tengwa series of their own, but are represented by column III letters with an added diacritic for following . Similarly shaped letters reflect not only similar places of articulation, but also similar manners of articulation. In the classical Quenya mode, row 1 represents voiceless stops, row 2 voiced prenasalized stops, row 3 voiceless fricatives, row 4 voiceless prenasalized stops, row 5 nasal stops, and row 6 approximants. Regularly formed Most letters are constructed by a combination of two basic shapes: a vertical stem (either long or short) and either one or two rounded bows (which may or may not be underscored, and may be on the left or right of the stem). These principal letters are divided into four series ("témar") that correspond to the main places of articulation and into six grades ("tyeller") that correspond to the main manners of articulation. Both vary among modes. Each series is headed by the basic signs composed of a vertical stem descending below the line, and a single bow. These basic signs represent the voiceless stop consonants for that series. For the classical Quenya mode, they are , , and , and the series are named tincotéma, parmatéma, calmatéma, and quessetéma, respectively; téma means "series" in Quenya. In rows of the general use, there are the following correspondences between letter shapes and manners of articulation: Doubling the bow turns the voiceless consonant into a voiced one. Raising the stem above the line turns it into the corresponding fricative. Shortening it (so it is only the height of the bow) creates the corresponding nasal. In most modes, the signs with shortened stem and single bow do not correspond to the voiceless nasals, but to the approximants. In addition to these variations of the tengwar shapes, there is yet another variation, the use of stems that are extended both above and below the line. This shape may correspond to other consonant variations required. Except for some English abbreviations, it is not used in any of the better known tengwar modes, but it occurs in a Quenya mode where the tengwa Parma with extended stem is used for and the tengwa Calma with extended stem is used for . The tengwar with raised stems sometimes occur in glyph variants that look like extended stems, as seen in the inscription of the One Ring. An example from the parmatéma (the signs with a closed bow on