Dyad stands for something that consists of two parts, something that can be divided on two separate parts.
Triad consists of 3 parts. Tetrad consists of 4 parts. Triad is often used in writing and poems.
In text structure, we have words, sentences and paragraphs. Paragraph is multiple sentences talking of one single point.
Paragraph usually has 3 to 5 sentences. Paragraph with 3 sentences is a triad. Four sentences would be tetrad.
If each paragraph had 3 or 4 sentences, it would likely be much easier to read given text.
Wall of text is most difficult to read. Its also most difficult to follow its points and words.
If there is space between every 3 or 4 sentences, it is much easier for eyes to follow.
The rule of triad or tetrad can be used to form paragraphs with 3 or 4 sentences put together.
But also, we must take into consideration number of words per paragraph. Its important that sentences arent long.
Number of words can form a triad if number of words can be divided by 3. Example: 18 words.
You will notice that in writing of this text, I have used 18 words per each paragraph here.
18 words are both dyad and triad, since number 18 can be divided by both 2 and 3.
When each paragraph has 18 words, it becomes easier to read than wall of text without any spacing.
Thus, one can space text by number of words, by number of sentences, or both of those two.
There is also character count, but it might not be necessary since its too much work to do.
But each paragraph must talk about one main point, each paragraph must have different point from other paragraphs.