不是英文，是拉丁文 quantum satis= sufficient quantity，就是（使）足量的意思。
1. 维基百科：Quantum satis (abbreviation q.s. or Q.S.) is a Latin term meaning the amount which is enough.
2.Genscript: Latin. quantum satis (as much as is enough). This term is used when bringing up a volumn or weight to the final measurement. Example: "Then q.s. to 2 liters".
其他来源略。
