de samenwerking
de-wordcooperation
/də ˈsaːmə(n)ˌʋɛrkɪŋ/
de samenwerkingen
Words ending in -ing are de.
De samenwerking verliep erg goed.
The cooperation went very well.
The de/het checker covers one word. The full platform covers vocabulary, grammar and all five DUO sections.