An acrostic is a poem or other word composition in which the first letter of each new line spells out a word, message or the alphabet. The term 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. When the last letter of each new line forms a word it is called a telestich; the combination of an acrostic and a telestich in the same composition is called a double acrostic.

Poetry, also called verse, is a form of literature that uses aesthetic and often rhythmic qualities of language − such as phonaesthetics, sound symbolism, and metre − to evoke meanings in addition to, or in place of, a prosaic ostensible meaning. A poem is a literary composition, written by a poet, using this principle.