An acrostic is a poem or other form of writing in which the first letter, syllable or word of each line, paragraph, or verse spells out a word of message. Acrostics were used as a mnemonic device to help people memorize more easily.
One of the most popular or familiar acrostics comes from the days of the early church. As persecution of believers grew because of their belief in Christ, an acrostic was devised to symbolize other believers in Christ. Those early believers used the Greek language to identify Jesus Christ, God's Son, Savior: Ιησούς Χριστός, Θεού Υιός, Σωτήρ. The English transliteration is Iesous CHristos, THeou Yios, Soter. These initials spelled out ICHTHYS which is the Greek word for fish. When a Christian saw either the acrostic letters ICHTHYS or the drawing of a fish, he or she knew that other Christians were present.
An abecedarius is an acrostic in which the first letter of every word, stanza, or verse follows the order to the alphabet. Abecedarius is also a generic term from an alphabet book. We have an example of this in the Psalms 119. Not only being the longest Psalm in the bible it uses successive letters of the Hebrew alphabet as the first letter of each verse. Many bibles are printed with the Hebrew letter as the head of the stanza or verse that begins each line with that Hebrew letter. Unfortunately the translators did not carry this over into English and we are unable to see the acrostic design of the Psalm. Let me share with you an example of the first eight verses of Psalm 119 as they would appear in the Hebrew:
A blessing is on them that are undefiled in the way
and walk in the law of Jehovah;
A blessing is on them that keep his testimonies,
and seek him with their whole heart;
Also on them that do no wickedness,
but walk in his ways.
A law hast thou given unto us,
that we should diligently keep thy commandments.
Ah! Lord, that my ways were made so direct
that I might keep thy statutes!
And then shall I not be confounded.
While I have respect unto all thy commandments.
As for me, I will thank thee with an unfeigned heart,
when I shall have learned thy righteous judgments.
An eye will I have unto thy ceremonies,
O forsake me not utterly.