‘De’ is always used for professions: ‘de kok’ (the chef), ‘de bewaker’ (the guard)
‘De’ tends to be used for people with an identified gender, such as: ‘de vader’ (the father), ‘de dochter’ (the daughter).
‘De’ is also used for vegetables, fruits, trees and plants, names of mountains and rivers
Furthermore, 'de' is also used for the words ending with -ie,- ij, -heid, -teit,-a, -nis, -st, -schap, -de, -te, -iek, -ica, -theek, -iteit, -tuur, -stuur, -sis, -xis, -tis, -ade, -ide, -ode, -ude, -age, -ine, -se, -ea, -esse
Finally, ‘de’ is used for written-out numbers and letters: ‘de drie’ (the three); ‘de a’ (the a).
'Het' is always used for a diminutive
‘Het’ is also always used for words consisting of two syllables and starting with be-, ge-, ver-, ont-
'Het' is always used for languages, names of metals, words ending with -isme, -ment and for words derived from verbs.
‘Het’ is used for names of compass points: ‘het noorden’ (the North).
'Het' is also used for the gerund: 'het zwemmen' (swimming), 'het dansen' (dancing), etc.
‘Het’ is used for names of sports and games: ‘het schaken’ (chess), ‘het voetbal’ (football)
'Het' is used for beginning and end: 'het begin' 'het einde'