International Journal of Neutrosophic Science IJNS 2690-6805 2692-6148 10.54216/IJNS https://www.americaspg.com/journals/show/3704 2020 2020 Laboratory of Pure and Applied Mathematics, Faculty of Mathematics and Computer Science, University of M’sila, University Pole, Raod Bordj Bou Arreridj, M’sila 28000, Algeria Soheyb Soheyb Laboratory of Pure and Applied Mathematics, Faculty of Mathematics and Computer Science, University of M’sila, University Pole, Raod Bordj Bou Arreridj, M’sila 28000, Algeria Lemnaouar Zedam Laboratory of Science for Mathematics, Computer Science and Engineering Applications, Department of Mathematics, University Center of Barika, Amdoukal Road, Barika, 05001, Algeria Soheyb Milles In this paper, we study the notion of principal (crisp) fuzzy ideals (resp. filters) on the setting of trellises (or weakly associative lattices as called by several authors). More specifically, we introduce the notions of L-fuzzy ideals and L-fuzzy filters on a given trellis and provide basic characterizations of these notions based on their weakly associative meet and join operations. We pay particular attention to the kind of principal L-fuzzy ideals (resp. filters) on a given trellis, which are more complicated in the absence of the (associativity) transitivity property. 2025 2025 164 181 10.54216/IJNS.260212 https://www.americaspg.com/articleinfo/21/show/3704