fetus: an unborn or unhatched vertebrate in the later stages of development showing the main recognizable features of the mature animal
vertebrate: animals having a bony or cartilaginous skeleton with a segmented spinal column and a large brain enclosed in a skull or cranium
person: a grammatical category used in the classification of pronouns, possessive determiners, and verb forms according to whether they indicate the speaker, the addressee, or a third party