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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.〔(【引用サイトリンク】title= Acrostic Poetry )〕 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").〔''Oxford English Dictionary'', 3rd ed., s.v. ''acrostic''; "The expected spelling of the English word, on the n., ''monostich'' n."〕 As a form of constrained writing, an acrostic can be used as a mnemonic device to aid memory retrieval. ==Overview== 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 songs that make up the Book of Lamentations, in the praise of the good wife in Proverbs 31, 10-31, and in Psalms 9, 10, 25, 34, 37, 111, 112, 119 and 145 of the Hebrew Bible. Notable among the acrostic Psalms are the long Psalm 119, which typically is printed in subsections named after the letters of the Hebrew alphabet, each of which is featured in that section; and Psalm 145, which is recited three times a day in the Jewish services. Acrostics prove that the texts in question were originally composed in writing, rather than having existed in oral tradition before being put into writing. Acrostics are common in medieval literature, where they usually serve to highlight the name of the poet or his patron, or to make a prayer to a saint. They are most frequent in verse works but can also appear in prose. The Middle High German poet Rudolf von Ems for example opens all his great works with an acrostic of his name, and his world chronicle marks the beginning of each age with an acrostic of the key figure (Moses, David, etc.). In chronicles, acrostics are common in German and English, though rare in other languages. Often the ease of detectability of an acrostic can depend on the intention of its creator. In some cases an author may desire an acrostic to have a better chance of being perceived by an observant reader, such as the acrostic contained in the ''Hypnerotomachia Poliphili'' (where the key capital letters are decorated with ornate embellishments). However, acrostics may also be used as a form of steganography, where the author seeks to conceal the message rather than proclaim it. This might be achieved by making the key letters uniform in appearance with the surrounding text, or by aligning the words in such a way that the relationship between the key letters is less obvious. This is referred to as ''null ciphers'' in steganography, using the first letter of each word to form a hidden message in an otherwise innocuous text. Using letters to hide a message, as in acrostic ciphers, was popular during the Renaissance, and could employ various methods of enciphering, such as selecting other letters than initials based on a repeating pattern (equidistant letter sequences), or even concealing the message by starting at the end of the text and working backwards. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Acrostic」の詳細全文を読む スポンサード リンク
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