• "The scientific study of population, including birth rate, death rate, and age structure" is known as - Demography.
• Demography (Noun):
- English meaning: The changing number of births, deaths, diseases, etc. in a community over a period of time; the scientific study of these changes
- Bangla meaning: জনসংখ্যা; জনতত্ত্ব;।
• Other options:
- Atmosphere: The mixture of gases that surrounds the Earth.
- Bangla meaning: বায়ুমন্ডল।
- Anthropology: The study of the human race, especially of its origins, development, customs and beliefs.
- Bangla meaning: নৃতত্ত্ব; নরবিজ্ঞান; মানুষের উৎপত্তি ও বিকাশ-সম্বন্ধীয় বিজ্ঞান; নরবিদ্যা;।
- Geography: The scientific study of the earth’s surface, physical features, divisions, products, population, etc..
- Bangla meaning: ভূগোলবিদ্যা।
Source: Merriam & Webster Dictionary, Oxford Dictionary, English-Bangla Dictionary.