I have noticed that on Stack Exchange sites, "week reputation" is referring to the reputation gained from Sunday to Saturday (in fact, my today's reputation is different from my week's reputation, and today is Monday).
I remember I asked to my friend, who is American, what she would consider the first day of the week, and she replied saying it is Monday.
Which word (or words) can I use instead of "the first day of the week?"
Best Answer
It depends on what you mean by "week" in this case.
In America, Sunday is considered the first day of the week, and Monday is considered the first day of the work week.
Note that SE sites end their week at the end of Saturday, GMT. This makes Sunday the first day of the SE week.
If you want to be safe you could just say "the start of the week," but you would still have to define what you meant by "week": the start of which week?