baseline
noun [ C usually singular ] uk/ˈbeɪs.laɪn/ us/ˈbeɪs.laɪn/
（网球场等的）底线
a line on a sports field, such as the one in tennis, that marks the end of the playing area, or the one in baseball that marks the path along which players run
She delivered a final serve from the baseline to win the match. 她从底线发出了致胜的一球。
（进行比较时用作起点的）基线
an imaginary line used as a starting point for making comparisons
a baseline assessment 基线评估；摸底评估