estrogen

This term refers to a class of steroid hormones that govern the development of female reproductive systems and secondary sex characteristics. It is typically discussed in medical or biological contexts regarding endocrine health, puberty, and menopause. As a chemical substance and a biological category, the word is treated as an uncountable noun. It does not have a plural form in standard usage, as it refers to the collective group of hormones or the general substance rather than individual countable units.