Théorie des magmoïdes

— The main opérations applied te trees, such as substitution, are axiomatically described by defining the algebraïc structure ofmagmoïd. Trees themselves can be defined then as éléments ofafree magmoïd. Thus it is possible to deal with tree languages theory in a more algebraïc way. We give hère a formai présentation of basic éléments of this theory and also an example of application.