A knit fabric is made by the longitudinal and vertical repetition of the same element, the loop, which is the basic element of the fabric.
When knitting is done by hand, the loops are held on one knitting needle and the yarn is pulled through each loop individually to form the new row of stitches. This row of stitches is subsequently connected to the next row. In machine knitting there is a needle for every stitch. Stitches are formed by the action of these needles that pull the yarn through the old loop to form the new stitch.
In weft knits the interloop links two consecutive loops placed horizontally; when one loop breaks, the entire fabric can be undone simply by pulling the free end of the yarn.
In warp knits the yarn is knitted vertically or diagonally and loops are formed accordingly; to knit the fabric, it is necessary to use many threads simultaneously, allowing the loops formed by the different threads to bind together. In this case, the knit fabric is ladder-proof.
From a physical point of view, a fabric can be described as a flexible structure, made up by the vertical and horizontal repetition of two elements: the course and the wale. The word “course” defines a row of horizontal loops, belonging or not to the same yarn; “wale” means a row of loops laid vertically one upon the other.