sun letter

noun Arabic Grammar.

any letter, as tā or sīn, representing a consonant that assimilates the l of a prefixed definite article.
Compare moon letter.

Origin of sun letter

translation of Arabic al-hurūf ash-shamsīyah, so called from the use of ash-shams “the sun” to illustrate assimilation of l to sh in al “the” Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019