أولا: لو معناها (منذ) يتبعها ماضي بسيط ولكن لا يتبع ذلك مستقبل
Sir, just read the following:
1- Since he travelled, he hasn't phoned me.
ثانيا: لو معناها (لأن) لا تتقيد بزمن وإنما حسب المعنى
Sir, just read the following:
2- Since we've got a few minutes to wait for the train, let's have a cup of tea.
ثالثا: (complete) قد تستخدم كمجهول أو كمعلوم
Sir, just read the following:
3- She will complete her studies in France.
4- The palace took over twenty years to complete.