since有对比的意思吗

没有对比的意思，since意思是自从……时候，例如：

1、You've grown since the last time I saw you!自从我上次见到你后，你又见长了！

2、She's a changed woman since she got that job.她自从得到了那份工作，变得判若两人。

3、I've lost six and a half pounds since I started my diet.从节食以来，我体重已减轻了六磅半。