In shacharit, we recite the 13 middot (already a strange word) through which a piece of Torah text is explained (explicated?) This comes from Braita d'Rav Yishma'el and, admittedly, I haven't look at this in the original; I am basing myself on the text in the Artscroll siddur.
The opening statement introduces the middot and the first item picks up on the language of the introduction saying "mikal vachomer" -- FROM a kal vachomer. The second says "umi'gezeirah shava" -- and FROM a gezeirah shava.
This makes syntactical sense because the intro said "these are the ways:" (paraphrase mine) so he list says "from x..."
But at item 6, the list omits the mem (from) so the item is not connected to the introduction. Number 7 resumes the mem but 8-13 do not begin with it. Aside from inconsistency, does this affect the way in which the item is understood or applied to a Torah text? Is it an arbitrary linguistic quirk or does it mean that the middah is used differently or understood as categorically different from the other items?