An acrostic is a poem or other form of writing in which the first letter, syllable or word of each line, paragraph or other recurring feature in the text spells out a word or a message. The word comes from the French acrostiche from post-classical Latin acrostichis, from Koine Greek ἀκροστιχίς, from Ancient Greek ἄκρος "highest, topmost" and στίχος "verse"). As a form of constrained writing, an acrostic can be used as a mnemonic device to aid memory retrieval.