Summary: We further contribute to the properties of fuzzy soft sets as defined and studied in the work of Maji et al. (2001), Roy and Maji (2007), and Yang et al. (2007), and support them with examples and counterexamples. We improve Proposition 3.3 of [P. K. Maji
, R. Biswas
and A. R. Roy
, J. Fuzzy Math. 9, No. 3, 589–602 (2001; Zbl 0995.03040
)]. Finally we define arbitrary fuzzy soft union and fuzzy soft intersection and prove De Morgan Inclusions and De Morgan Laws in Fuzzy Soft Set Theory.