Recently the study of intentional goal-directed behavior has re-gained interest in the field of animal behavior. Numerous studies investigate intention in e.g. animal communication, social tactics, and tool use. Still, a clear and unified understanding of goal-directed intentions in humans and animals is lacking. The topic of intentionality has been of interest since the scholastics and received much attention in philosophy starting with Brentano who marked intentionality as the hallmark of the mental. Ever since Dennett and his proposal of the levels of intentionality in the animal realm, the notion of intentionality as intentional goal-directed behavior has been used in comparative ethology. While cognitive sciences aim to find intentionality as well as goal-directed intentions in humans and animals, criminal law had to introduce a functional description in order to deal with criminal intent, mental capacity, and diminished responsibility. Comparative ethology is trying to find a formalization of the concept in order to be able to investigate intentions empirically in animals. Different disciplines have working and functional descriptions of intent that might help cognitive ethologists to formalize the ability to have goal-directed intentions for non-linguistic animals. Evaluations and comparisons of concepts of intention between the disciplines – comparative ethology, criminal law, philosophy, and psychology are presented. Intentional behavior, forming an intention, and forms of intentions will be discussed. Additionally I will provide a concept of intentionality for future empirical investigations in the formation of intentions and goal-directed behavior in animals and humans that might also help to understand theory of mind in a broader perspective. By comparing the theoretical background of the disciplines I anticipate to help develop a better framework for empirical work.