IPA: /ˌmɛn.səˈreɪ.ʃən/
KK: /mɛnˈsʌr eɪ ʃən/
The process or art of measuring different geometric quantities such as lengths, areas, or volumes.
In mathematics class, we learned about mensuration and how to calculate the area of various shapes.
Mensuration is formed from "mensurare" (meaning to measure) and the suffix "-tion" (indicating the action or process of). The word refers to the process of measuring, particularly in mathematics and geometry.
Think of 'measuring' ('mensurare') as the main action, and remember that 'mensuration' is all about the process of measuring.