stone
n. C / Un. a hard, solid piece of rock that you find on the ground. It can also mean the hard seed in the middle of fruits like peaches or cherries.
n. a hard, solid, non-metallic mineral matter of which rock is made. In a botanical context, it refers to the hard endocarp of a drupe fruit containing the seed.
The boy threw a small stone into the river.
The ancient walls were built using heavy grey stone found in the local mountains.
Geologists analyzed the composition of the stone to determine whether the formation resulted from volcanic activity or sedimentary deposits over millions of years.
Uncountable when referring to the material; countable when referring to individual pieces of rock or fruit seeds.
The house is made of stones.The house is made of stone.When referring to building material, the word is uncountable and should be used in the singular form.