And first, although there were more things in nature then words which did expresse them, yet even in these mute and silent discourses, to expresse complexed significations, they took a liberty to compound and piece together creatures of allowable formes unto mixtures inexistent […]
Source: wiktionary
1978, David A. Bloestein, Introduction, John Marston, David A. Bloestein (editor), Parasitaster: Or, The Fawn, page 47,
Both these formes, with running titles intact, were retained to print sheet D of Q2.
Source: wiktionary
1994, Jay L. Halio, Introduction, Jay L. Halio (editor), William Shakespeare, The First Quarto of King Lear, page 21,
Q2 was printed in twenty-two formes.
Source: wiktionary
In casting off, the printing house would judge the length of a manuscript to determine both how many sheets would be needed, and what the divisions were between one forme and another. (A forme is one side of a sheet: four quarto pages or two folio pages.) Because formes do not have many consecutive pages, estimates would be further broken down by page. If a quarto forme includes a putative page one, for instance, that side of the sheet would also include pages four, five, and eight.
Source: wiktionary