a sedimentary rock consisting mainly of calcium that was deposited by the remains of marine animals
"The ancient coral reefs formed from limestone, a sedimentary rock consisting mainly of calcium that was deposited by the remains of marine animals."
An abundant rock of marine and fresh-water sediments; primarily composed of calcite (CaCO₃); it occurs in a variety of forms, both crystalline and amorphous.
"The construction project used local limestone because its abundance as a sedimentary rock made up mainly of calcite provided the necessary strength for the foundation."
In plain English: Limestone is a hard rock made mostly of shells and bones that forms underwater layers over millions of years.
"We used limestone to build the foundation for our new house."
Usage: Do not confuse "limestone" with "limestone," the latter being an archaic or misspelled variant. This term refers strictly to the geological rock type and should not be used metaphorically for softness or whiteness in casual speech.
The word limestone is a straightforward compound formed by combining the words lime and stone to describe rock containing calcium carbonate. It entered English as a descriptive term that directly reflects its composition rather than undergoing any significant shift in meaning over time.