A more thorough explanation:

FOETUS

A developing but unborn mammal, especially in the latter stages of development. It is also spelled as fetus. It is different from an embryo and a zygote.

- The foetus of a human baby is fully formed by the end of the second trimester.
- The ultrasound showed that the foetus was healthy and growing properly.
- The mother could feel the foetus moving inside her womb.

These examples illustrate the definition of foetus as a developing but unborn mammal. The first example shows that the foetus is fully formed by a certain stage of development. The second example shows that medical technology can be used to monitor the health and growth of the foetus. The third example shows that the foetus is alive and active inside the mother's womb.