Pneumatology is the study of spiritual beings and phenomena, especially the spiritual aspect of human beings and the interactions between humans and God. Pneuma is Greek for "breath", which metaphorically describes a non-material being or influence. Pneumatology as the study of the spirit is to be distinguished from psychology, the study of the soul. As many religious denominations do not distinguish between soul and spirit, this has been somewhat problematic. In general, the ABCs of psychology are the study of cognition, affect, and connation, or to put it into words more generally recognized, thinking, feeling, and willing. Thoughts, feelings, and acts of will (motivations, intentions, willfulness) is what fills the psyche, but when psychology is done what is primarily of interest is the actual nature of the collecting, organizing, and clarifying of thoughts, that is, thinking characterized as cogent, logical, run-on, disconnected, tautologous, symbolic, or psychotic (schizophrenic). Similarly feelings may be brought to the center of attention, but in psychology what is of interest is the actual nature of feeling itself, characterized as intuitive, sympathetic, empathic, inappropriate, projective, easily changeable, fixed and not easily changeable, or psychotic (manic-depressive). Similarly a person's will acts may be considered, but in psychology it is the actual nature of using the will that is of interest, characterized as unconscious, weak, self-serving, magnanimous, informed by thinking and feeling, overly influential over thinking and feeling, or psychotic (psychopathic or sociopathic). In contradistinction to psychology, pneumatology involves the study of the spirit (German Geist, Greek pneuma). In general, the ABCs of pneumatology are the study of technique (craftsmanship, German Kunst, Greek techne), science (conceptualization of ideas, German Wissenshaft, Greek episteme), poetry (inspiration, German Einatmung, Greek poises), belief (opinion, German Glaube, Greek doxa), and recognition (holding in mind, German Erkenntnis, Greek gnosis).

In Christian theology pneumatology refers to the study of the Holy Spirit. The English word comes from two Greek words: πνευμα (pneuma, spirit) and λογος (logos, teaching about). Pneumatology would normally include study of the person of the Holy Spirit, and the works of the Holy Spirit. This latter category would normally include Christian teachings on new birth, spiritual gifts (charismata), Spirit-baptism, sanctification, the inspiration of prophets, and the indwelling of the Holy Trinity (which in itself covers many different aspects). Different Christian denominations have different theological approaches.