Having reached full natural growth or development

Trưởng thành / hoàn thiện

Ex: The eggs hatched and the chicks matured

_to turn from something solid into something soft or liquid, or to causesomething to do this

_Example: 

Melt the chocolate slowly so that it doesn't burn.

Definition: a period of 1000 years (thiên niên kỉ)

Example: The year 2000 was an example of the millennium.