FHN said- Im looking at your chart again, Adam. Let me point out that the picture representing the word foetus is of an embryo.
FHN, sorry for not providing a link to the commonly-accepted definitions used in medicine and biology; the pix was chosen as a short-cut so as not to get buried down in the details, but since you asked, here's the wikipedia page which discusses the stages of life for human development:
http://en.wikipedia.org/wiki/Human_development_%28biology%29
We can go to more heavy-duty medicine-based sources, if you want....
On the embryo vs fetus distinction:
In humans, the embryo is referred to as a fetus in the later stages of prenatal development. The transition from embryo to fetus is arbitrarily defined as occurring 8 weeks after fertilization. In comparison to the embryo, the fetus has more recognizable external features, and a set of progressively developing internal organs.
Also, note this:
Childbirth is the process in which the baby is born. Age is defined relative to this event in most cultures.
Physical stages
There are no universal definitions for terms of age-related physical development stages, but following are some approximate age ranges:
Stages in prenatal development.
- Prenatal (sperm fertilizes egg - birth)
- Embryo - fertilization - 8 weeks after fertilization)
- Zygote, the single cell stage which occurs after fertilization
- Blastocyst, the stage prior to implantation, when the embryo is a hollow sphere
- Post-implantation embryo, the period 1 – 8 weeks after fertilization (3 to 10 weeks gestation)
- Fetus, (10th week of pregnancy - birth)
- Embryo - fertilization - 8 weeks after fertilization)
Approximate outline of development periods in child development.
- Childhood/Juvenile (Childbirth)(0 - 19)
Further information: Child development and Child development stages
- Neonate (newborn) (0 – 30 days)
- Infant (baby) (0 month - 12 months)
- Toddler (1 – 3 years)
- Play age (4–5 years)
- Primary school age (middle childhood also called prepubescence) (4-12)
- Elementary school age (6-12)
- Preadolescence (preteen.The child in this and the previous phase are called schoolchild (schoolboy or schoolgirl), when still of primary school age.) (10 – 12 years)
- Adolescence and puberty (13 – 19 years)
- Adulthood (20+ years)
- Young adulthood (20 – 39 years)
- Middle adulthood (40 – 59 years)
- Advanced adulthood/Senior citizen (60+ years)
- Death (occurs at various ages, depending on person)
- Decomposition (breakdown of the body after death)