been (benen) leg(s)
knoop (knopen) button(s)
THINGS MENTIONED IN THE INSTRUCTIONS
patroondelen pattern pieces
tweelingnaald twin needle
rekbaar stretchy (if the describtion doesn't mention 'jersey' or 'tricot' this usually refers to wovens with some stretch)
ben. stof abbreviation of 'benodigde stof'= 'fabric needed' used by Knipmode
This is by no means a complete list but it's kind of hard for me to guess which terms would help and which would be useless. So if you are using Dutch sewing magazines without knowing the language, and you come across any words that might explain things better but are not in my list, please leave a comment. Just state the words you need to have translated and I'll try to explain them and make updates of this list.