When a solid turns into a liquid it is called fusion, more commonly referred to as melting. When a material moves from one state of matter into another it is called a phase transition. Fusion is just...
Human pregnancy can be divided roughly into three trimesters, each approximately three months long. The first trimester is from the last period to the 13th week, the second trimester is from the 14th to 27th week, and the third trimester is from the 28th week to the 42nd week. In humans, birth normally occurs at a gestational age of about 40 weeks, though it is common for births to occur from 37 to 42 weeks.
The weeks are grouped into three pregnancy trimesters. The first one of the trimesters of pregnancy is from week 1 to week 12, the second is from week 13 to week 27, while the third trimester of pregnancy lasts from week 28 to the birth.