A subtotal is the total of one part of a longer list of numbers — a total that is not the final total. On a receipt in a shop, you see the prices of all the things you bought added up, and that number is the subtotal; then tax is added, and maybe a service charge or a discount, and only then do you get the real total at the bottom. So a subtotal is honest but unfinished: it is a true sum of what it covers, and it is waiting for more numbers to come. The word is mostly used for money and for spreadsheets. In a spreadsheet you might add up each month's sales, and each of those monthly numbers is a subtotal; the year's number is the total. It is also a verb, used mainly by people doing accounts: "subtotal each column first, then add the columns." As a verb it is quite technical and you will hear it far less than the noun. It does not carry any feeling — nobody uses it to mean "a small amount" or "not enough." A subtotal can be a huge number. The "sub-" is only about position in the adding-up, not about size.

小計（收據上稅前的那一行；不是「總計」，總計是加完稅之後最下面那個數字）