This couplet variant is named the "crystalline" because the core value of the form is its highly condensed and concrete imagery, transparent in its accessibility. The fact that the name breaks down to "crystal - line" is serendipitous. A primary concern for the crystalline is the euphony of the verse. The technical criteria are really very simple. The hard part, the fun part, the real art, is developing a good ear for a euphonious verse. Nothing works here except practice. Of course, for those who are already accomplished poets and have highly developed ears for a pleasingly modulated line, the challenge may be simply in fitting a lovely line to this strict form.

      • A crystalline is a couplet, titled or untitled, rhymed or unrhymed, seventeen syllables in length, consisting in two lines of either iambic or trochaic tetrameter, with very minor variations permissible. The couplet must have exactly seventeen syllables, with deference granted the poet for dialectical variations in pronunciation.

      • The couplet must be complete in itself, not dependent for its meaning on additional stanzas. Even when linked (see below for linking), such autonomy is definitive for the crystalline form.

      • The couplet should consist in one or two sentences. Initial capitalization of the first word of a sentence, a proper name, etc., should follow common usage. Do not capitalize the first word of the second line solely on the basis of its position. Terminal punctuation also should follow common usage.

      • An essential is natural English diction, carefully modulated for euphony. The harmony or beauty of sound that has a pleasing effect to the ear is achieved both by the selection of individual word-sounds and also by their relationship in the repetition, proximity, and flow of sound patterns. This is euphony, more important than strict metrics. Skillful word selection to modify the rhythmic pattern, i.e., modulation, is desirable. The grammar (inflections and syntax) of the lines, which usually comprise one or two sentences in a couplet, should be relatively straightforward and natural. Unnaturally abbreviated or telegraphic grammar is to be avoided. The traditional omission of "understood words" is permissible (e.g., "Catch me." rather than "You catch me.").

      • All traditional English poetic devices (including, but not limited to, metaphor, simile, alliteration, assonance, consonance, onomatopoeia, allusion, rhyme) which can be used to advantage within the other rules and the set prosody are permissible. In such a short form, verbosity is to be avoided. Poets should strive for highly condensed and concrete imagery that enhances perception and understanding. Transparency of meaning need not diminish the depth of poetic resonance.

      • Crystallines may be linked by one poet or by more than one poet. A crystalline in such a sequence is an untitled stanza, which follows a strict syllabic verse form, as described in the previous paragraphs, that is, several crystallines may be linked together as stanzas of a larger poem. Alternating crystallines by different poets may be combined in a single poem. This is not to debar a single poet writing a linked poem, which is entirely permissible. In any such linked crystalline, each couplet must be autonomous, able to stand on its own, yet each couplet must be closely related to its following and preceding couplets; the internal links are substantial so that the whole poem has a poetic unity.