-id

1) (in psychoanalysis) a part of the unconscious mind governed by the instinctive forces of libido and the death wish. These violent forces seek immediate release in action or in symbolic form. The id is therefore said to be governed by the pleasure principle and not by the demands of reality or of logic. In the course of individual development some of the functions of the id are taken over by the ego. n.

2) relationship or resemblance to. suffix denoting

spermatid — a stage of sperm formation