IPA: //ˈmɛnstrum//
KK: /ˈmɛnstrum/
A substance that is used to dissolve another substance, often used in chemistry or medicine to extract compounds from materials.
In the laboratory, the chemist used a menstruum to extract essential oils from the plant.
Menstruum is derived from the Latin "mensis" (meaning month) and the suffix "-trum" (indicating a means or instrument). The term originally referred to a monthly cycle, particularly in relation to the menstrual cycle, and has come to denote a solvent or medium in which substances are dissolved.
Think of the word 'month' ('mensis') to remember that 'menstruum' relates to a cycle, particularly the monthly cycle, and also serves as a medium for dissolving substances.