number of lines (bat, , , from Pali and Sanskrit pāda), depending on the type. The bat are subdivided into two wak (, , from Sanskrit varga). The first wak has five syllables, the second has a variable number, also depending on the type, and may be optional. The type of khlong is named by the number of bat in a stanza; it may also be divided into two main types: khlong suphap (, ) and khlong dan (, ). The two differ in the number of syllables in the second wak of the final bat and inter-stanza rhyming rules. Khlong si suphap The khlong si suphap (, ) is the most common form still currently employed. It has four bat per stanza (si translates as four). The first wak of each bat has five syllables. The second wak has two or four syllables in the first and third bat, two syllables in the second, and four syllables in the fourth. Mai ek is required for seven syllables and Mai tho is required for four, as shown below. "Dead word" syllables are allowed in place of syllables which require mai ek, and changing the spelling of words to satisfy the criteria is usually acceptable. The following plan shows the rhyming structure of one stanza. Each letter represents a syllable; A and B (also C, D, E and F in other examples) represent rhyming syllables. Syllables shown by letters in parentheses are optional. The following plan shows the tone mark requirements; each ◌ represents one syllable. Example Transcriptions: Translation: Chan The chan (, from Pali chando), is derived from Pali and Sanskrit metres, and based on the Vuttodaya, a Sri Lankan treatise on Pali prosody. It developed during the Ayutthaya period, and became a prominent poetic form, but declined afterwards until it resurfaced in a 1913 revival. The main feature of the chan is its requirements on the "heaviness" of each syllable. Syllables are classified as either "light" (lahu, , ), those with a short vowel and open ending, or "heavy" (kharu, , ; See also Light and heavy syllables under Sanskrit prosody). The Thai metres follow their Pali/Sanskrit origins, with added rhyming schemes. Modern authors have also invented new forms for their compositions. Two traditional forms are shown here. Inthrawichian chan The inthrawichian chan (, , from Indravajra, a form of Sanskrit poetry and meaning Indra's thunderbolt) has two bat