Merithal is a unique word that requires a bit of explanation when it comes to spelling. It is pronounced /mɛrɪθæl/ with emphasis on the first and third syllables. The "e" in the second syllable is pronounced as a short "i" sound, and the "a" in the fourth syllable is pronounced as a short "u" sound. The "th" in the ending syllable is pronounced as a "th" sound rather than a "t" sound. Although the word may seem unfamiliar at first, with proper pronunciation it can easily become part of one's vocabulary.
In bot., a term used in place of internode; a term applied to the different parts of the leaf.
Etymological and pronouncing dictionary of the English language. By Stormonth, James, Phelp, P. H. Published 1874.