noun, plural: embryos
(zoology) A multicellular organism that primarily undergoes extensive and rapid growth and differentiation between the time of fertilization and fetal stage in higher forms while larval stage in lower forms
(human biology) Baby in the early developmental stage, after the zygote phase (at fertilization) to week eight from the time of fertilization (note: week eight from the time of fertilization is equivalent to 10 weeks gestational age)
In humans, the embryo refers to the growing organism after being a zygote and before being a fetus. The zygote becomes an embryo immediately after series of cell division. After the continuous cell division and differentiation in eight weeks, the embryo becomes a fetus in which the organism undergoes extensive organogenesis.
Word origin: Ancient Greek embruon (fetus), from en-, in- + bruō (grow, swell)