A stone is an old English measurement of 14 pounds
The abbreviation for stone as a weight measurement is st.
A physical rock "A stone" is indeed matter. However the weight measurement "stone" is not matter, it is a unit of measurement (which is applied to matter).
The English used to use actual stones as weights to place in balances to weigh large quantities of materials.
It means half a stone. This is not a difficult concept. (It helps to know that a "stone" is a traditional English measurement of weight equivalent to 14 pounds, so half of one would be 7 pounds.)
In the English Imperial measurement system, 1 stone is 14 pounds
1 stone = 14 pounds
The pound (lb) is the same as in the US. Other units used in the UK are the stone, 14lb, the hundredweight, 112 lb, and the ton, 2240 lb. However these traditional units are now largely phased out in favour of metric units.
old system of measurement English system of measurement
Fifteen stone is a unit of weight measurement commonly used in the United Kingdom. One stone is equivalent to 14 pounds, so fifteen stone is equal to 210 pounds.
Stone
J. C. Evans has written: 'Late lamps' 'Measurement of angle in engineering' 'The stone corn' -- subject(s): English poetry