An acrostic is a poem (or other form of writing) in which the first letter (or syllable, or word) of each line (or paragraph, or other recurring feature in the text) spells out a word, message or the alphabet. 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.

Relatively simple acrostics may merely spell out the letters of the alphabet in order; such an acrostic may be called an 'alphabetical acrostic' or Abecedarius. These acrostics occur in the first four of the five chapters that make up the Book of Lamentations, in the praise of the good wife in Proverbs 31, 10-31, and in Psalms.

An acrostic poem written in English by Edgar Allan Poe is entitled simply "An Acrostic":

Elizabeth it is in vain you say

"Love not"—thou sayest it in so sweet a way:

In vain those words from thee or L.E.L.

Zantippe's talents had enforced so well:

Ah! if that language from thy heart arise,

Breath it less gently forth—and veil thine eyes.

Endymion, recollect, when Luna tried

To cure his love—was cured of all beside—

His follie—pride—and passion—for he died.

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