Let Fq denote the finite field of order q, let m1, m2, · · · , m ℓ be positive integers satisfying gcd(mi, q) = 1 for 1 ≤ i ≤ ℓ, and let n = m1 + m2 + · · · + m ℓ . Let Λ = (λ1, λ2, · · · , λ ℓ ) be fixed, where λ1, λ2, · · · , λ ℓ are non-zero elements of Fq. In this paper, we study the algebraic structure of Λ-multi-twisted codes of length n over Fq and their dual codes with respect to the standard inner product on F n q . We provide necessary and sufficient conditions for the existence of a self-dual Λ-multi-twisted code of length n over Fq, and obtain enumeration formulae for all self-dual and self-orthogonal Λ-multi-twisted codes of length n over Fq. We also derive some sufficient conditions under which a Λ-multi-twisted code is LCD. We determine the parity-check polynomial of all Λ-multi-twisted codes of length n over Fq and obtain a BCH type bound on their minimum Hamming distances. We also determine generating sets of dual codes of some Λ-multi-twisted codes of length n over Fq from the generating sets of the codes. Besides this, we provide a trace description for all Λ-multi-twisted codes of length n over Fq by viewing these codes as direct sums of certain concatenated codes, which leads to a method to construct these codes. We also obtain a lower bound on their minimum Hamming distances using their multilevel concatenated structure.Theorem and the results derived in Ling and Solé [12]. They also obtained an improved lower bound on their minimum Hamming distances. Güneri et al. [6] decomposed GQC codes as direct sums of concatenated codes, which leads to a trace formula and a minimum distance bound for GQC codes. Jia [9] decomposed quasi-twisted (QT) codes and their dual codes over finite fields to a direct sum of linear codes over rings, and provided a method to construct quasi-twisted codes by using generalized discrete Fourier transform. Saleh and Esmaeili [16] gave some sufficient conditions under which a quasi-twisted code is LCD. In a recent work, Aydin and Halilovic [1] introduced multi-twisted (MT) codes as generalization of quasi-twisted codes. They studied basic properties of 1-generator multi-twisted codes and provided a lower bound on their minimum Hamming distances. The family of multi-twisted codes is much broader as compared to quasi-twisted and constacyclic codes.Throughout this paper, let F q denote the finite field of order q, and let Λ = (λ 1 , λ 2 , · · · , λ ℓ ) be fixed, where λ 1 , λ 2 , · · · , λ ℓ are non-zero elements of F q . Let n = m 1 + m 2 + · · ·+ m ℓ , where m 1 , m 2 , · · · , m ℓ are positive integers coprime to q. The main aim of this paper is to study the algebraic structure of Λ-multi-twisted codes of length n over F q and their dual codes with respect to the standard inner product on F n q . Enumeration formulae for their two interesting subclasses, viz. self-dual and self-orthogonal codes, are also obtained. These enumeration formulae are useful in the determination of complete lists of inequivalent self-dual and self-orthogonal Λ-multitwisted codes [7, Section 9.6...