Stock investment vs Fixed investment

(a)  Stock Investment:-
 Additions to the stock of raw material, semi-finished goods and finished goods during a year is called stock investment or inventory investment. Such a stock at the beginning of the year is called opening stock. The stock that exists at the end of the year is called closing stock. Suppose the relevant year is from April 1, 1997 to March 31, 1998, the stock of raw material, semi-finished goods and finished goods that exists on April 1, 1997 is called opening stock. The stock of these goods on March 31, 1998 is called closing stock. The excess of closing stock over the opening stock is called inventory investment. However, it is possible that during a particular year the production may be less than consumption. It implies that the closing stock is less than the opening stock. This is called negative investment or disinvestment.
(b) Fixed Investment:-
Acquiring up of durable use producer goods by production units is called fixed investment. It amounts to adding, new machines, equipment etc.
Total investment equals the sum of inventory investment and fixed investment. The alternative name for investment is capital formation.