Transducers and the Power of Delay -- When the Map is More Exact than the Terrain -- Formal Languages and the NLP Black Box -- On Structural Tractability Parameters for Hard String Problems -- Jumping Automata over Infinite Words -- Isometric Words based on Swap and Mismatch Distance -- Set Augmented Finite Automata over Infinite Alphabets -- Fast detection of specific fragments against a set of sequences -- Weak Inverse Neighborhoods of Languages -- The exact state complexity for the composition of Root and reversal -- Bit catastrophes for the Burrows-Wheeler Transform -- The Domino problem is undecidable on every rhombus subshift -- Synchronization of Parikh Automata -- Completely Distinguishable Automata and the Set of Synchronizing Words -- Zielonka DAG Acceptance and Regular Languages over Infinite Words -- On Word Representable and Multi-Word Representable Graphs -- On the Simon's Congruence Neighborhood of Languages -- Tree-Walking-Storage Automata -- Rewriting rules for arithmetics in alternate base systems -- Synchronizing Automata with Coinciding Cycles -- Approaching Repetition Thresholds Via Local Resampling and Entropy Compression -- Languages Generated by Conjunctive Query Fragments of FC[REG] -- Groups whose word problems are accepted by abelian G-automata.

This book constitutes the refereed proceedings of the 27th International Conference on Developments in Language Theory, DLT 2023, held in Umeå, Sweden, during June 12-16, 2023. The 20 full papers included in this book were carefully reviewed and selected from 32 submissions (31 regular ones and one invited).The DLT conference series provides a forum for presenting current developments informal languages and automata. Its scope is very general and includes, among others, the following topics and areas: grammars, acceptors and transducers for words; trees and graphs; relations between formal languages and artificial neural networks; algebraic theories of automata; algorithmic, combinatorial, and algebraic properties of words and languages; variable length codes; symbolic dynamics; cellular automata; groups and semigroups generated by automata; polyominoes and multidimensional patterns; decidability questions; image manipulation and compression; efficient text algorithms; relationships to cryptography, concurrency, complexity theory, and logic; bio-inspired computing; and quantum computing.