I was just looking at some timber screws online and was confused about the sizing. For example, the dimensions of one screw were, "18 - 7 x 200mm". Another one was 14g x 150mm. From what I understand, the first number in both cases refers to the diameter, 7 to the number of threads per inch/mm (not given in the second example), and then the length. Are the units used for the diameter the same in both examples (i.e, could the "18" in the first example also be written 18g)?
Here are links to product pages for each of the screws: